Component video

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Three cables, each with RCA plugs at both ends, are often used to carry YPbPr analog component video. Component-cables.jpg
Three cables, each with RCA plugs at both ends, are often used to carry YPbPr analog component video.

Component video is an analog 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 composite video in which all the video information is combined into a single signal that is used in analog television. Like composite, component cables do not carry audio and are often paired with audio cables.

Contents

When used without any other qualifications, the term component video usually refers to analog YPBPR component video with sync on luma (Y) found on analog high-definition televisions and associated equipment from the 1990s through the 2000s when they were largely replaced with HDMI and other all-digital standards. Component video cables and their RCA jack connectors on equipment are normally color-coded red, green and blue, although the signal is not in RGB. YPbPr component video can be losslessly 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.

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. For most consumer-level video applications, the common three-cable system using BNC or RCA connectors analog component video was used. Typical formats are 480i (480 lines visible, 525 full for NTSC) and 576i (576 lines visible, 625 full for PAL). For personal computer displays the 15 pin DIN connector (IBM VGA) provided screen resolutions including 640×480, 800×600, 1024×768, 1152×864, 1280×1024.

RGB analog component video

A 15-pin VGA connector for a personal computer Vga-cable.jpg
A 15-pin VGA connector for a personal computer
A 21-pin SCART or JP21 connector for a television SCART 20050724 002.jpg
A 21-pin SCART or JP21 connector for a television

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 a lot of redundant data since each channel typically includes much of the same black-and-white image. Early personal computers such as the IBM PS/2 offered this signal via a VGA port. Many televisions, especially in Europe, can utilize RGB via the SCART connector. All arcade video games, other than early vector and black-and-white games, use RGB monitors.[ 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 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.

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.

Luma-based analog component video

YPBPR component video out on a consumer electronics device, a Sony DVD player. Component video jack.jpg
YPBPR component video out on a consumer electronics device, a Sony DVD player.

Further types of component analog video signals do not use separate red, green and blue components but rather a colorless component, termed luma, which provides brightness information (as in black-and-white video). This combines 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 subsampling, a method used by JPEG and MPEG 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.

Connectors used

Synchronization

Component video requires an extra synchronization signal to be sent along with the video. Component video sync signals can be sent in several different ways:

Separate sync
Uses separate wires for horizontal and vertical synchronization. When used in RGB (i.e. VGA) connections, five separate signals are sent (Red, Green, Blue, Horz. Sync, Vert. Sync).
Composite sync
Combines horizontal and vertical synchronization onto one pair of wires. When used in RGB connections, four separate signals are sent (Red, Green, Blue, Sync).
Sync-on-green (SOG)
Combines composite sync with the green signal in RGB. Only three signals are sent (Red, Green with Sync, Blue). This synchronization system is used in - among other applications - many systems by Silicon Graphics and Sun Microsystems through a DB13W3 connector.
Sync-on-luminance
Similar to sync-on-green, but combines sync with the luminance signal (Y) of a color system such as YPbPr and S-Video. This is the synchronization system normally used in home theater systems.
Sync-on-composite
The connector carries a standard composite video signal along with the RGB components, for use with devices that cannot process RGB signals. For devices that do understand RGB, the sync component of that composite signal is used along with the color information from the RGB lines. This arrangement is found in the SCART connector in common use in Europe and some other PAL/SECAM areas.

Digital component video

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 such as 480p, 480i, 576i, 576p, 720p, 1080i, and 1080p. [1]

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, [2] higher dynamic range, and can be made to support digital 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.

International standards

Examples of international component video standards are:

Component versus composite

In a composite signal, such as NTSC, PAL or SECAM, the luminance, Brightness (Y) signal and the chrominance, Color (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 and B-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.

See also

Related Research Articles

<span class="mw-page-title-main">Analog television</span> Television that uses analog signals

Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, phase and frequency of an analog signal.

<span class="mw-page-title-main">Chrominance</span> Colour in an image or video

Chrominance is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal. Chrominance is usually represented as two color-difference components: U = B′ − Y′ (blue − luma) and V = R′ − Y′ (red − luma). Each of these difference components may have scale factors and offsets applied to it, as specified by the applicable video standard.

<span class="mw-page-title-main">RGB color model</span> Color model based on red, green and blue

The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additive primary colors, red, green, and blue.

<span class="mw-page-title-main">Digital Visual Interface</span> Standard for transmitting digital video to a display

Digital Visual Interface (DVI) is a video display interface developed by the Digital Display Working Group (DDWG). The digital interface is used to connect a video source, such as a video display controller, to a display device, such as a computer monitor. It was developed with the intention of creating an industry standard for the transfer of uncompressed digital video content.

<span class="mw-page-title-main">Video Graphics Array</span> Computer display standard and resolution

Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the IBM PC compatible industry within three years. The term can now refer to the computer display standard, the 15-pin D-subminiature VGA connector, or the 640 × 480 resolution characteristic of the VGA hardware.

<span class="mw-page-title-main">SCART</span> 21-pin connector for audio-visual equipment

SCART is a French-originated standard and associated 21-pin connector for connecting audio-visual (AV) equipment. The name SCART comes from Syndicat des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs, "Radio and Television Receiver Manufacturers' Association", the French organisation that created the connector in the mid-1970s. The related European standard EN 50049 has then been refined and published in 1978 by CENELEC, calling it péritelevision, but it is commonly called by the abbreviation péritel in French.

<span class="mw-page-title-main">Y′UV</span> Mathematical color model

Y′UV, also written YUV, is the color model found in the PAL analogue color TV standard. A color is described as a Y′ component (luma) and two chroma components U and V. The prime symbol (') denotes that the luma is calculated from gamma-corrected RGB input and that it is different from true luminance. Today, the term YUV is commonly used in the computer industry to describe colorspaces that are encoded using YCbCr.

<span class="mw-page-title-main">Composite video</span> Analog video signal format

Composite video is an analog video format that typically carries a 525 or 625 line signal on a single channel, unlike the higher-quality S-Video and the even higher-quality component video.

<span class="mw-page-title-main">S-Video</span> Signal format for standard-definition video

S-Video is an analog video signal format that carries standard-definition video, typically at 525 lines or 625 lines. It encodes video luma and chrominance on two separate channels, achieving higher image quality than composite video which encodes all video information on one channel. It also eliminates several types of visual defects such as dot crawl which commonly occur with composite video. Although it improved over composite video, S-Video has lower color resolution than component video, which is encoded over three channels.

A DVD player is a device that plays DVDs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. Some DVD players will also play audio CDs. DVD players are connected to a television to watch the DVD content, which could be a movie, a recorded TV show, or other content.

<span class="mw-page-title-main">Chroma subsampling</span> Practice of encoding images

Chroma subsampling is the practice of encoding images by implementing less resolution for chroma information than for luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance.

<span class="mw-page-title-main">D-1 (Sony)</span> Magnetic tape-based videocassette format

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<span class="mw-page-title-main">Color Graphics Adapter</span> IBM PC graphic adapter and display standard

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<span class="mw-page-title-main">VGA connector</span> 15-pin video connector

The Video Graphics Array (VGA) connector is a standard connector used for computer video output. Originating with the 1987 IBM PS/2 and its VGA graphics system, the 15-pin connector went on to become ubiquitous on PCs, as well as many monitors, projectors and high-definition television sets.

<span class="mw-page-title-main">YPbPr</span> Color space used in video electronics

YPbPr or Y'PbPr, also written as YPBPR, is a color space used in video electronics, in particular in reference to component video cables. Like YCbCr, it is based on gamma corrected RGB primaries; the two are numerically equivalent but YPBPR is designed for use in analog systems while YCBCR is intended for digital video. The EOTF may be different from common sRGB EOTF and BT.1886 EOTF. Sync is carried on the Y channel and is a bi-level sync signal, but in HD formats a tri-level sync is used and is typically carried on all channels.

<span class="mw-page-title-main">Composite monitor</span>

A composite monitor or composite video monitor is any analog video display that receives input in the form of an analog composite video signal to a defined specification. A composite video signal encodes all information on a single conductor; a composite cable has a single live conductor plus earth. Other equipment with display functionality includes monitors with more advanced interfaces and connectors giving a better picture, including analog VGA, and digital DVI, HDMI, and DisplayPort; and television (TV) receivers which are self-contained, receiving and displaying video RF broadcasts received with an internal tuner. Video monitors are used for displaying computer output, closed-circuit television and other applications requiring a two-dimensional monochrome or colour image.

GameCube accessories include first-party releases from Nintendo, and third-party devices, since the GameCube's launch in 2001.

Audio connectors and video connectors are electrical or optical connectors for carrying audio or video signals. Audio interfaces or video interfaces define physical parameters and interpretation of signals. For digital audio and digital video, this can be thought of as defining the physical layer, data link layer, and most or all of the application layer. For analog audio and analog video these functions are all represented in a single signal specification like NTSC or the direct speaker-driving signal of analog audio.

Various accessories for the PlayStation 2 video game console have been produced by Sony, as well as third parties. These include controllers, audio and video input devices like microphones and video cameras, and cables for better sound and picture quality.

References

  1. "What Shared Composite/Component Video Connections On TVs Mean For You". lifewire.com. Retrieved 21 March 2018.
  2. "HDMI 2.1a Specification Overview". www.hdmi.org. Retrieved 2023-08-04.
  3. "Video Signal: Composite vs. Component". Apple Support. 3 October 2008. Retrieved 25 April 2011.