The first computers used modified television screens, this is due to the fact that in the middle of the Cold War it was feared that the radio frequency system of these could be modified with computers for matters of espionage or access. to radio communications used from the rear then. This led to the sale of computer terminal screens without the possibility of adjustment, but at the same time allowed the implementation of proprietary video input and output connectors.
Until the arrival of PC AT in 1984 which brought the EGA standard, PC monitors were modified NTSC television screens, however, the limitations of this format when displaying images at higher definition have necessitated the adoption of new PC monitor formats with higher horizontal frequency. than NTSC 15.7KHz. At this point, the path of TVs and monitors was 20 years apart until the arrival of monitors and LCD TVs, however, the difference remains the same, the lack of inclusion of a TV tuner in the monitor.
In this article, we will talk about the evolution of input and output connectors for monitors and, therefore, we will focus on those found on PCs. So we are not going to talk about video outputs such as S-Video, Component, Composite, SCART and many others that can be seen on the rear panel of many TVs.
Obsolete video outputs
The connectors in this section are the ones that can still be seen in many computers, but due to the emergence of more advanced technologies they have fallen into disuse. In other words, they have been replaced and they will not evolve, so if you find a monitor or a graphics card with this type of connection, believe us that it is very old and that it will not provide acceptable performance today. ‘hui.
Puerto VGA
Every PC from the 90s and the first half of the 2000s used the VGA, an RGB type video connector, since it sent the color component information in three different channels, the connector also has the pins to control horizontal synchronization and vertical monitor, which at the time was controlled by the graphics card itself. The sync pins indicate that this is a port designed for monitors that use a cathode ray tube to generate the image.
Being a port for a PC monitor, it does not carry audio and this is because when VGA first appeared on the PC, the internal speaker was used or, failing that, the new ones. sound cards to reproduce audio, not monitors. , which, as you may have deduced, had no ability to reproduce sound.
Due to its analog nature, no one gets along with LCD panels, which has led to the need to create a digital interface in order to achieve good picture quality. The reason why this happens is related to the analog to digital signal converter which results in loss of information during conversion when using a VGA port.
Puerto DVI (digital video interface)
Over time, LCD panels became cheaper and users started buying them because they saved desk space compared to conventional tube monitors. Although the different nature of the display of the image on the screen necessitated changes in the video outputs on PCs, hence the birth of DVI.
The differences with the VGA? For starters, it assigns two pins to each of the three RGB channels, although it is a digital port, it retains the HSync and VSync pins, but they are hardly used. In fact, it does this with a series of pins from which the monitor sends the information about resolution and refresh rate, in this way the signal sending is auto-configured and the use of sync pins is not is not necessary. The first ports that appeared were DVI-I, as they have the pins for use in analog monitors, but over time DVI-D has been standardized, which is only intended for LCDs as it lacks pins for LCD screens. screens.
There were two different generations of DVI video connectors, on the one hand the SL with a maximum resolution of 1920 x 1200 pixels and on the other the DL with a resolution of 2560 x 1600 pixels also at 60 Hz. DVI never supported variable frequency rate and over time it was quickly replaced by HDMI and DisplayPort.
Video outputs used today
The video outputs that we are going to talk about next are those that can be found in graphics cards and PC monitors today. The fact that the panels are the same on flat screen televisions and monitors has completely universalized the video interfaces and therefore the different connectors.
HDMI port
The most used today and with nearly twenty years of evolution has gone from the presentation of images to 720p version 1.0 to resolutions 8K with 2.1, which represents an increase of 50 times more pixels compared to its origin. In its evolution we have seen additions such as support for various aspect ratios, variable frequency rate, HDR, etc.
The HDMI port was born as a variant of DVI, but it does not match in its design and shape, as well as in the distribution of pins. The differences with DVI? Since it was created as a video output for audiovisual content, it can carry audio and also contains video for HDCP, the content protection system still used by the audiovisual industry today.
HDMI cable is designed to give lossless signal with distance up to 5 meters, much greater distance between output signal and input signal ends up causing loss in signal quality, it is therefore important to keep the PC as close to the monitor as possible if such a video connector is used.
DisplayPort or DP
The other most used video connector in monitors and PC graphics cards is called DisplayPort, which like HDMI has gone through several different generations in its evolution until today. The big difference is that they were born out of two different standards committees and that’s why DisplayPort is seen more on monitors than TVs. Also, including this port is often a good way to tell if a display is a TV or a monitor.
The big difference between HDMI and DisplayPort apart from their shape and pin distributions is that HDCP support for some content is not mandatory in a DP interface, that means for video game consoles and players video this type of connector It is not used, as this is essential for the reproduction of commercial audiovisual content. This is why DisplayPort has today become a port associated with the PC. However, unlike DVI and VGA and like HDMI, DisplayPort also has the ability to transmit audio.
DisplayPort via USB
The most recent of the video outputs is a variant of USB-C, which uses its huge bandwidth to transmit the video signal, at the same time as it is used to transmit data through the USB 2.0 pins and also serves as power. the monitor. It may become the most used port in the future by allowing the display to do without the AC adapter and make them fully portable, of course, this will require the bandwidth to exceed HDMI 2.1, which is already available with the ‘USB 4.0 based on Thunderbolt.
For the moment, it is a port of minority use, in any case, everything indicates that the DisplayPort is closer to extinction than the HDMI, since it has all the numbers to be replaced by USB-C ports. with the possibility of transmitting video.
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