New Technologies DVI - Digital Video Interface

DVI or Digital Video Interface - is a new form of video interface technology made to fully maximise flat panel LCD monitors and high-end video graphics cards. It is Capable of high bandwidths required to support very high resolution screens and offers a replacement for the 'Plug & Display' standard and a step-up from the digital-only DFP format for older flat panels. DVI is becoming increasingly popular with video card manufacturers and most cards purchased nowadays include both a VGA and a DVI output port.

There are three types of DVI connections:

• DVI-D (Digital)
• DVI-A (Analogue)
• DVI-I (Integrated Digital/Analogue)

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

DVI-A offers high resolution analogue definition and is used to carry a DVI signal to an analogue display, such as a CRT monitor or an HDTV. Although some signal quality is lost from the digital to analogue conversion, it still transmits a higher quality picture than standard VGA.

DVI-I offers the best of both worlds and is a hybrid carrier in that it combines an integrated cable which is capable of transmitting either a digital-to-digital signal or an analogue-to-analogue signal. However it will not work for transmitting a digital-to-analogue or analogue-to-digital signal. The connection ensures backwards-compatibility with analogue signals and forwards-compatibility with digital signals. This allows users to upgrade to digital graphics and enjoy even better visual performance, as and when they want to.

Note: Like any other format, DVI digital and analogue formats are non-interchangeable. This means that a DVI-D cable will not work on an analogue system, nor a DVI-A on a digital system. Only equipment with a DVI port labelled 'DVI-I' will accept both a DVI-D and DVI-A source signal.

Single & 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 cables send information using a digital information format called TMDS (Transition Minimised Differential Signalling).

Single 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. With dual link it is possible to obtain a resolution of 2048 x 1536 pixels. This ability to achieve high bandwidth and larger resolutions has pushed DVI into the forefront of graphics technology.

	< The type of DVI lead necessary to connect components (such as the type sold as good electrical stores such as Maplin - www.maplin.co.uk - in the UK
The DVI card found in computers and high-end LCD monitors. Shown here is the female DVI socket >
VGA socket (female) and below is the DVI (male) socket
	< Male connectors of the various sorts of DVI plugs

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