Component video
Component video is an
When used without any other qualifications, the term component video usually refers to analog
Analog component video
Reproducing a video signal on a display device (for example, a
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 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, 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
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
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
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
- D-Terminal: Used mostly on Japanese electronics.
- Three BNC (professional) or RCA connectors (consumer): Typically colored green (Y), blue (PB) and red (PR).
- SCART used in Europe.
- Mini-DIN.
Synchronization
Component video requires an extra
- Separate sync
- Uses separate wires for horizontal and vertical synchronization. When used in VGA) connections, five separate signals are sent (Red, Green, Blue, Horz. Sync, Vert. Sync).
- Composite sync
- Combines horizontal and vertical synchronization onto one wire. When used in RGB connections, only four separate signals are sent (Red, Green, Blue, Comp. 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
International standards
Examples of international component video standards are:
- /TIA-343)
- RS-343RGB (525, 625 or 875 lines)
- STANAG 3350 Analogue Video Standard (NATO military version of RS-343 RGB, now EIA-343A)
- CEA-770.3 High Definition TV Analog Component Video Interface Consumer Electronics Association
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
References
- ^ "What Shared Composite/Component Video Connections On TVs Mean For You". lifewire.com. Retrieved 21 March 2018.
- ^ "HDMI 2.1a Specification Overview". www.hdmi.org. Retrieved 2023-08-04.
- ^ "Video Signal: Composite vs. Component". Apple Support. 3 October 2008. Retrieved 25 April 2011.
External links
- Poynton, Charles (November 28, 2006). "Color FAQ- Frequently Asked Questions about Color". Retrieved 2009-06-28.
- VGA to Sync-On-Green adapter — circuit to convert VGAsync to sync-on-green.
- CS150 - Spring 1999 - Composite Video Project describes video timing principles.