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The Digital Visual Interface (DVI) is a video interface standard designed to maximize the visual quality of digital display devices such as flat panel LCD computer displays and digital projectors. It was developed by an industry consortium, the Digital Display Working Group (DDWG). more...

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It is designed for carrying uncompressed digital video data to a display. It is partially compatible with the High-Definition Multimedia Interface (HDMI) standard in digital mode (DVI-D).

Overview

The DVI interface uses a digital protocol in which the desired illumination of pixels is transmitted as binary data. When the display is driven at its native resolution, it will 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 pixels as well as by electrical noise and other forms of analog distortion.

Previous standards such as the analog VGA were designed for CRT-based devices and thus did not use discrete time display addressing. As the analog source transmits each horizontal line of the image, it varies its output voltage to represent the desired brightness. In a CRT device, this is used to vary the intensity of the scanning beam as it moves across the screen.

DVI cable connectors are designed in such a way as to not allow the user to connect the cable in an incorrect position or orientation. DVI connectors are available in five models, differing in the way they handle analog or digital transfers.

In the digital transfer one or two channels are present. Video and monitor cards which are exclusively digital cannot be connected to analog, but can be connected to equipment that handles both analog and digital signals. The DVI standard also supports the Display Data Channel (DDC) and the Extended Display Identification Data (EDID) which allows computers to communicate with different monitor extensions.

"DVI-I" stands for "DVI-Integrated" and supports both digital and analog transfers, so it works with both digital and analog monitors. "DVI-D" stands for "DVI-Digital" and supports digital transfers only.

Technical discussion

The data format used by DVI is based on the PanelLink serial format devised by the semiconductor manufacturer Silicon Image Inc. This uses Transition Minimized Differential Signaling (TMDS). A single DVI link consists of four twisted pairs of wire (red, green, blue, and clock) to transmit 24 bits per pixel. The timing of the signal almost exactly matches that of an analog video signal. The picture is transmitted line by line with blanking intervals between each line and each frame, and without packetization. No compression is used and there is no support for only transmitting changed parts of the image. This means that the whole frame is constantly re-transmitted. The specification (see below for link) does, however, include a paragraph on "Conversion to Selective Refresh" (under 1.2.2), suggesting this feature for future devices.

Read more at Wikipedia.org