Digital Video out cable
Component video is a 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 is transmitted or stored as three separate signals. Component video can be contrasted with (NTSC, PAL or SECAM) in which all the video information is combined into a single line-level signal that is used in analog television. Like composite, component-video cables do not carry audio and are often paired with audio cables.
When used without any other qualifications the term component video usually refers to analog YPBPR component video with sync on luma.
Analog component video
Reproducing a video signal on a display device (for example, a cathode 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 and YPBPR signals comprise two or more separate signals, and thus are all component-video signals. In the past, for most consumer-level applications, analog component video was used; however, digital component video became increasingly more common in both computer and home-theater applications. Component video is capable of carrying various signals, such as 480i, 480p, 576i, 576p, 720p, 1080i, 1080p, 2040p and beyond. Many new high definition TVs support the use of component video up to their native resolution.
RGB analog component video
The various RGB (red, green, blue) analog component video standards (e.g., RGBS, RGBHV, RGsB) use no compression and impose no real limit on color depth or resolution, but require large bandwidth to carry the signal and contain much redundant data since each channel typically includes much of the same black-and-white image. Most modern computers offer this signal via a VGA port. Many televisions, especially in Europe, utilize RGB via the SCART connector. All arcade games, other than early vector and black-and-white games, use RGB monitors.
RGB component video has largely been replaced by modern digital formats, such as DisplayPort or Digital Visual Interface (DVI) digital connections, while home theater systems increasingly favor High-Definition Multimedia Interface (HDMI), which support higher resolutions, higher dynamic range, and can be made to support digital rights management. The demise of VGA 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 analogue and back again for a flat digital display, particularly when used at higher resolutions where analog signals are highly susceptible to noise. RGB has never been common in North America for consumer electronics as S-Video was considered sufficient for consumer use, although RGB was used extensively in commercial, professional and high-end installations.
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, where the horizontal and vertical signals are mixed together on a separate wire (the S in RGBS)
- separate sync, where the horizontal and vertical are each on their own wire (the H and V in RGBHV; also the acronym HD/VD, meaning horizontal deflection/vertical deflection, is used)
- sync on green, where a composite sync signal is overlaid on the wire used to transport the green signal (SoG, Sync on G, or RGsB).
- sync on red or sync on blue, where a composite sync signal is overlaid on either the red or blue wire
- sync on composite (not to be confused with composite sync), where the signal normally used for composite video is used alongside the RGB signal only for the purposes of sync.
- sync on luma, where the Y signal from S-Video is used alongside the RGB signal only for the purposes of sync.
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 with VGA, used worldwide for analog computer monitors. This is sometimes known as RGBHV, as the horizontal and vertical 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 their PlayStation 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.