What is DVI?

 

 Back To Tutorial Home

DVI (Digital Visual Interface) was developed by the industry body DDWG (the Data Display Working Group) to send digital information from a computer to a digital display, such as a flat-panel LCD monitor. DVI uses TMDS (transition minimized differential signaling) to transmit large amounts of digital data from the source to the display, resulting in a high-quality image. DVI technology successfully moved from the computer marketplace to the audio/video realm, and is now found on many high-end TVs, DVD players, and HDTV set-top boxes.

DVI took a step forward with HDMI, which integrates audio and video into a more compact interface. The DVI interface uses a connector that resembles a DB-style connection. However, instead of round pins, the DVI connector uses flattened pins that appear “twisted” at an angle. This design is referred to as an LFH (low force helix) connector. The peculiar shape of the pins ensures a good contact with the mating connector. DVI connectors use thumbscrews for retention.

 

The DVI connector on a device is therefore given one of three names, depending on which signals it implements:

 

DVI-A (Analog Only)   DVI-I (Digital and Analog)   DVI-D (Digital Only)

DVI-A Male

  

DVI-I Male Single-Link

  

DVI-D Male Single-Link
One set of eight pins and one set of four pins, with four contacts around the blade   Two sets of nine pins and four contacts around the blade   Two sets of nine pins, and a solitary flat blade
   

DVI-I Male Dual-Link

  

DVI-D Male Dual-Link
    Three rows of eight pins and four contacts around the blade   Three rows of eight pins and a solitary flat blade

 

DVI-Analog

are used to carry a DVI signal to an analog display, such as a CRT monitor or budget LCD. The most common use of DVI-A is connecting to a VGA device, since DVI-A and VGA carry the same signal. There is some quality loss involved in the digital to analog conversion, which is why a digital signal is recommended whenever possible.

 

DVI-I

are integrated cables which are capable of transmitting either a digital-to-digital signal or an analog-to-analog signal. This makes it a more versatile cable, being usable in either digital or analog situations.

 

DVI-D

are used for direct digital connections between source video (namely, video cards) and digital LCD (or rare CRT) monitors. This provides a faster, higher-quality image than with analog, due to the nature of the digital format. All video cards initially produce a digital video signal, which is converted into analog at the VGA output. The analog signal travels to the monitor and is re-converted back into a digital signal. DVI-D eliminates the analog conversion process and improves the connection between source and display.

Single and Dual Links

The Digital formats are available in DVI-D Single-Link and Dual-Link as well as DVI-I Single-Link and Dual-Link format connectors.

These DVI cables send information using a digital information format called TMDS (transition minimized differential signaling). Single link cables use one TMDS 165Mhz transmitter, while dual links use two. The dual link DVI pins effectively double the power of transmission and provide an increase of speed and signal quality; i.e. a DVI single link 60-Hz LCD can display a resolution of 1920 x 1080, while a DVI dual link can display a resolution of 2048 x 1536.

   
Back To Top of Page Back To Tutorial Home
Disclaimer