Digital Visual Interface (DVI)

Introduction

Digital Visual Interface (DVI) is a type of cable and connection developed in 1999 by the Digital Display Working Group (DDWG), which is a cooperative of technology companies led by Intel, Fujitsu, IBM, Compaq, NEC, Hewlett-Packard, and Silicon-Image, with the intention to meet increased bandwidth and performance demands.

What is DVI?

DVI is a video interface standard designed to maximise the visual quality of digital display devices such as flat screen LCD, computer displays and digital projectors.

A DVI interface connection can transfer a digital video signal from a source component directly to a video display which has a DVI connection, eliminating the needs of conversion to analog. This can result in a better quality image from both standard and high definition video signals as each conversion create small amounts of signal loss which impact the overall quality of the picture.

DVI Technology

DVI transfers data through an interface known as Transition Minimized Differential Signaling (TMDS). DVI specifications call for at least one TMDS "link" to transmit data, though there are DVI specifications that have what's called dual links or two TMDS channels. A single link has three data channels (RGB) and one clock control channel. In some cases two or "dual" TMDS links may be used to increase the bandwidth of the connection.

A 10-bit TMDS link operates at up to 165 MHz and offers 1.65Gbps of bandwidth. This is enough to operate a digital flat panel display at 1920 x 1080 resolution refreshed at 60 Hz. This is virtually doubled with a dual link TMDS. Dual offers 2Gbps of bandwidth but must be operated at 100 MHz to match the second link with the primary link. Its possible to get a resolution of 2048 x 1536 with a dual link TMDS. This ability to achieve high bandwidth and larger resolutions has pushed DVI into the forefront of graphics technology.

How does DVI works?

The DVI interface uses a digital protocol in which the desired brightness of pixel is transmitted as binary data. When the display is driven at its native resolution, all it has to do is read each number and apply that brightness to the appropriate pixel. In this way, each pixel in the output buffer of the source device corresponds directly to one pixel in the display device, whereas with an analog signal the appearance of each pixel may be affected by its adjacent pixel as well as by electrical noise and other forms of analog distortion.

Benefits of DVI

Processing large amounts of data at high speed
DVI is the fastest way to transfer data or video. It beats every other connectivity standard hands down. It has a 24-bit digital RGB interface that can support computer resolutions as high as 1600 x 1200 (UXGA), and the cinematic-apex, 1080 progressive high definition format. In fact, it is capable of supporting even higher bandwidth using a Dual Link.

Better quality image
DVI, being a digital interface suffers none of the problems traditionally associated with analogue interfaces, such as noise, “sparkles”, “ghosting”, “snow”, poor colour matching and “softness” caused by loss of sharpness.

Support both analog and digital connections
DVI is able to support both analog and digital connections. DVI-D is a smaller connector, and supports only digital signals. DVI-I is slightly larger and can accommodate both digital and analog signals.