Component Video

Component video is a video signal that has been split into two or more components. In popular use, it refers to a type of analog video information that is transmitted or stored as three separate signals. Component video can be contrasted with composite video (NTSC, PAL or SECAM) in which all the video information is combined into a single line-level signal. Like composite, component video cables do not carry audio. Reproducing a video signal on a display device (for example, a 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. S-Video, RGB and YPbPr signals comprise two or more separate signals: hence, all are 'component video' signals. For most consumer-level applications, analog component video is used. Digital component video is slowly becoming popular in both computer and home-theatre applications.

Component video is capable of carrying signals such as 480i, 480p, 576i, 576p, 720p, 1080i and 1080p, although many TVs do not support 1080p through component video. Most modern computers offer this signal via the VGA port. All arcade games, excepting early vector and black and white games, use RGB monitors. Analog RGB is slowly falling out of favor as computers obtain better clarity using digital (DVI) video and home theater moves towards HDMI. RGB requires an additional signal for synchronizing the video display. Several methods are used, i.e. composite sync, where the horizontal and vertical signals are mixed together on a separate wire, separate sync, where the horizontal and vertical are each on their own wire and sync on green, where a composite sync signal is overlaid on the green wire. Sometimes a full composite video signal may also serve as the sync signal, though often computer monitors will be unable to handle the extra video data. A full composite sync video signal requires four wires – red, green, blue, sync. If separate cables are used, the sync cable is usually colored white. Separate sync is most common with VGA, used worldwide for analog computer monitors. If separate cables are used, the sync lines are usually yellow, white, yellow and black, or gray and black. Further types of component analogue video signals do not use R,G,B components but rather a colorless component, termed luma, combined with one or more color-carrying components, termed chroma, that give only color information.

Both the S-Video component video output (two separate signals) and the YPbPr component video output (three separate signals) seen on DVD players are examples of this method. Converting video into luma and chroma allows for chroma sub-sampling, a method used by JPEG images and DVD players to reduce the storage requirements for images and video. Many consumer DVD players, high-definition displays, video projectors and the like, use this form of color coding. In component video systems, additional synchronization signals may need to be sent along with the images. In computing, the common standard is for two extra wires to carry the horizontal and vertical components or separate syncs', whereas in video applications it is more usual to embed the sync signal in the Y' component or sync on luma. 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.