Connection technology most widely used in TVs, monitors and video projectors currently is HDMI, but you can still find equipment based on old standards VGA, DVI, S-Video and Component Video (Component Video).
This text was prepared to quickly explain the main characteristics of these patterns and, consequently, to make clear what are the differences between them.
VGA (Video Graphics Array) connector
VGA (see abbreviationfinder for its meanings of Video Graphics Array) connectors were developed in the 1980s by IBM and are well known, as they were present in the absolute majority of “big” tube monitors (CRT – Cathode Ray Tube), as well as being implemented in the first LCD monitors.
The VGA connector, whose name is D-Sub or DB Connector, is composed of three “rows” of five pins. These pins are connected to a cable whose wires independently transmit information about the colors red (red), green (green) and blue (blue). The combination of these colors, also known as the RGB scheme, results in the images displayed on the screen.
It is also up to the VGA cable to transmit information about frequencies. The horizontal frequency is the number of lines on the screen that the monitor can “fill” per second. Thus, when a monitor can scan 60 thousand lines, we say that its horizontal frequency is 60 KHz.
There is also the vertical frequency or refresh rate, which is the time it takes the monitor to go from the top left of the screen to the bottom right.
Thus, if the horizontal frequency indicates the number of times the monitor can scan lines per second, the vertical frequency indicates the number of times the screen as a whole is scanned per second. If it is traversed, for example, 56 times per second, we say that the vertical frequency of the monitor is 56 Hz.
By definition, VGA connections support up to 70 Hz refresh rate and screen resolutions up to 800×600 pixels (thanks to SVGA, discussed below), although 640×480 pixel resolution was the most common at the time this standard was common.
It is worth mentioning that many monitors came with VGA cables with missing pins. It was not a defect: although VGA connectors have a 15-pin socket, not all of them were always used.
SVGA (Super Video Graphics Array)
You can also find references to SVGA (Super VGA). It is essentially an improved version of VGA presented by VESA (Video Electronics Standards Association) to support higher resolutions. The connectors, however, have not changed.
Because of its proposal to increase the resolution supported by the standard, it is common for the acronym SVGA or the name Super VGA to be used to designate the resolution of 800×600 pixels.
DVI (Digital Video Interface) connector
Unveiled in the late 1990s, DVI (Digital Video Interface) connectors were, at least to some extent, considered a replacement for the VGA standard. This is because, as its name implies, the image information can be treated in a totally digital way here, which is not the case with the VGA standard.
When, for example, an LCD monitor works with VGA connectors, it needs to convert the signal it receives to digital. This process has the side effect of reducing the image quality.
Since DVI works directly with digital signals, there is no need to convert, so the image quality is maintained. For this reason, the DVI output was widely used in video monitors, projectors, TVs, among other video equipment.
It should be noted that the industry has adopted more than one type of DVI connector:
DVI-A: it is a type that uses analog signal, but offers image quality superior to the VGA standard. The ‘A’ in DVI-A is for Analog (analog);
DVI-D: it is a type similar to DVI-A, but uses digital signal, which is why DVI-D is also known as DVI Digital. It is also more common than its similar because it has been widely implemented in video cards ;
DVI-I: this standard can work with both DVI-A and DVI-D. Because of this convenience, DVI-I was widely adopted by the industry. The ‘I’ in the acronym comes from Integrated.
There are also DVI connectors that work with Single Link and Dual Link specifications. The first supports resolutions up to 1920×1080 pixels and the second supports resolutions up to 2060×1600 pixels, both with a frequency of up to 60 Hz.
The cable of devices using the DVI standard is basically composed of four pairs of twisted wires, one pair for each primary color (red, green and blue) and one for synchronism.
Despite bringing great advances in relation to VGA, such as higher resolutions and support for wider screens, DVI was gradually being replaced by HDMI, being even compatible with this: you can have a cable with a DVI connector on one end and HDMI on the other.
S-Video (Separated Video) connector
To understand S-Video (Separated Video), it is better to know another standard beforehand: Compost Video, better known as Composite Video. This type uses RCA type connectors (Radio Corporation of America) and was commonly found on TVs, DVD players, camcorders, among others.
Generally, equipment with Composite Video makes use of three cables, two for audio (left channel and right channel) and the third for video. This last cable is formed by two wires: one is responsible for the transmission of the image itself while the other acts as “ground”.
The S-Video, in turn, has a single cable formed by three segments: one transmits signal with parameters of brightness and “structure” in black and white; another sends color information; the third acts as land. It is this division of functions that made S-Video receive the name Separated Video.
The connector of the S-Video standard is known as Mini-Din and is usually formed by four pins. It is also possible to find seven-pin S-Video connections, which indicates that the device can also have Component Video (seen below).
Many video cards offered VGA or DVI connection with S-Video. Depending on the case, it was possible to find the three types of connection on the same board.
It is worth mentioning that S-Video appeared in the 1980s, it is completely analog and supports resolutions 480i (in NTSC) and 576i (in PAL).
The Component Video standard, or, in good Portuguese, Component Video, was widely used in computers for professional work (such as video editing), but its use was more common in DVD players, Blu-ray, high definition TVs and systems home theater.
Component Video is connected using a “triple” cable, one of which is usually identified with green, the other is indicated by blue and the third is given red, in a scheme known as Y-Pb-Pr (or Y-Cb-Cr).
The first (green), is responsible for transmitting brightness and structure parameters in black and white of the image. The rest of the connectors work with color data and timing. They must be fitted to the connectors with matching colors (green with green, blue with blue, red with red).
In order to connect a device to the computer using Component Video, it was necessary to use a special cable: one of its ends contained the Y-Pb-Pr connectors, while the other had a unique slot to be inserted in the video card.
Component Video is an analog standard and, as a rule, has a higher quality than S-Video, being able to work with resolutions such as 1080i and 1080p, although resolutions 480p, 576i, 576p and 720p were much more frequent in equipment compatible with this standard.