Video Connections Info (For Projectors and Monitors)

From VGA to HDMI Guide

Computer display standards

VGA, DVI, HDMI and DisplayPort are computer display standards. A standard is typically associated with certain video connectors, expansion cards and monitors.

The standards consists of the following.

• • Aspect ratio

  • Display size

  • Display resolution

  • Color depth

  • Refresh rate

Analog vs digital

Computer display standards can be analog or digital. An analog signal is a continuous signal in which two variables change in time in a dependent manner. For example, in an analog audio signal, the changes in voltage depend on the pressure of sound waves.

A digital signal is a signal that consists of discrete values such as 0 and 1. The word discretemeans separate. Applied to signals, it means that a signal can contain a set of numbers or values that stand apart, as opposed to being continuous.

Why did the switch to digital happen?

Digital signals have two main benefits over analog signals.

The first benefit is that digital signals can carry more information. Since an analog signal is continuous, it is impossible to throw information out of it even if it is not necessary. A digital signal is discrete and can contain only the needed information.

The second advantage of digital signals is that they are better at maintaining quality. With analog signals, if a signal is amplified, the noise is also amplified. While noise can add random information to a digital signal, too, the electronics can ignore the noise. This means that the quality of the signal can stay consistently high.

VGA

VGA is short for Video Graphic Array. Originally, it described display hardware manufactured by IBM and used in IBM PS/2 line of personal computers starting from 1987.

The hardware became so popular that the term VGA became synonymous with an analog computer display standard, the 15-pin 3-row VGA connector and the 640×480 screen resolution of the VGA displays.

Fundamentally, VGA standard became the lowest possible denominator for all PC graphics hardware. The original VGA standard specifications were up to 800 horizontal pixels and up to 600 vertical lines with 16-bit or 256-bit color and 256 kilobytes of video ram.

Today, most manufacturers have switched to other standards and do not use the VGA analog interface (not to be confused with the original VGA screen resolution standard) with the blue 3-row 15-pin VGA connector. However, there was a time (around 2010 or so) when manufacturers were using VGA analog interface for the transmission of high-definition video.

The term high-definition applies to video that has 720 horizontal lines or more and an aspect ratio of 16:9. It includes formats such as 1080i, 1080p, 1440p, 4K UHDTV and 8K UHD.

When you connect an old computer to a newer TV and go from, say, VGA to HDMI, it is possible that a picture from your device will not be able to scale to fit the screen of the TV entirely or you will have a mismatch between aspect ratios. If this happens, you have several options. You can try and find a setting that works for both the computer and the TV, show only a part of the picture on the TV screen, or have black bars at the sides of the TV.

In North America, most common standard definition video signal has 576 lines and 50Hz refresh rate.

There are no standards that describe the connection between quality of the video and the interface. Typically, to transmit higher quality signal, you will need a higher quality cable with coaxial wiring and insulation.

The phasing out of the VGA chipset support and switching to digital alternatives started to occur around 2010. Large manufacturers, such as Intel and AMD, stopped supporting the format by 2015. This means that if your computer or a TV screen was manufactured around 2010, it is likely to have a VGA connector.

If you bought a computer or a TV after 2015, it probably has a connector of one of the different formats you will read about below.

DVI

DVI is short for Digital Visual Interface. It was created in 1999 by Digital Display Working Group with the goal of transmitting uncompressed digital video between displays and display controllers, such as computers and gaming consoles. Notice that the term DVI applies only to a video display interface. Unlike VGA, the term was never associated with screen resolutions or computer display standards.

The DVI interface is fully compatible with the VGA interface, which is why some of the pins in a DVI connector carry analog VGA signals. It is the only popular video standard with analog and digital signal support in the same connector. In contrast, its competitors, such as LVDS, switched to digital right away.

DVI connectors

There are several types of DVI connectors. The type of connector depends on what kind of signal the connector carries.

DVI-I combines digital and analog signals in the same connector.

DVI-D carries digital signals only (hence the letter D in its name).

DVI-A carries only analog signals.

Connectors that carry digital video signals (DVI-I and DVI-D) can be single link or digital link. You can use single link connectors with resolutions of up to 1920 x 1200 at 60Hz. Dual link connectors have more pins compared to single link connectors and can support up to 2560 x 1600 at 60Hz or 3,840 x 2,400 at 33 Hz (Note: dual link connection has nothing to do with dual monitors, which is a separate subject). Manufacturers sometimes call dual link connectors DVI-DL,DL being an abbreviation for Dual Link.

DVI format can support analog signals, digital signals, or a combination of digital and analog. This compatibility led to the widespread usage of the DVI format. In the early 2000s, DVI became popular with manufacturers of computers, TV screens, and DVD players.

Because DVI is compatible with VGA, adapters from one interface to the other are very inexpensive. VGA monitors are also very easy to connect to computers and other devices that have DVI video source interface.

Intel and AMD made the announcement about stopping their support for DVI at the same time they announced phasing out the support for VGA in December of 2010. The timeline was also the same for VGA and DVI. Intel and AMD planned to complete the transition by 2015.

How did analog to digital converters work?

Analog to digital converters replace each real number from the analog signal with a number from a finite set of discrete values.