DVI

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...

Home
Amplifiers
Audio Accessories & Cables
Cable TV
DVD Players & Recorders
Digital Video Recorders, PVR
Gadgets & Other Electronics
Home Audio
Home Theater Projectors
Home Theater in a Box
Radios: CB, Ham & Shortwave
Satellite Radio
Satellite TV
Telephones & Pagers
Televisions
Accessories & Cables
Other
TV Antennas
TV Stands
Video Cables
Adapters, Converters
Analog
Digital, Non-HDTV
HDTV
HDTV Cables
S-Video Cables
Standard Cables
Coaxial
Component
Composite (RCA)
DVI
Other
S-Video
Video Selectors, Switches
Wall Mounts & Brackets
Direct-View Standard TVs
DVD/VCR Combo TVs
HDTV Receivers, Tuners
HDTVs, Direct-View
LCD Flat-Panel TVs
Other
Plasma TVs
Portable TVs
Rear Projection TVs
VCRs
Vintage Electronics

It is designed primarily for carrying uncompressed digital video data to a display. It is partially compatible with the HDMI standard.

Overview

The DVI interface uses a digital protocol in which the desired brightness 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. 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.

However, when using digital displays (such as LCD) with analog signals (such as VGA), there is an array of discrete pixels and a single brightness value must be chosen for each. The decoder does this by sampling the voltage of the input signal at regular intervals. When the source is also a digital device (such as a computer), this can lead to distortion if the samples are not taken at the center of each pixel, and there are also problems with crosstalk.

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 DVI does not yet have a specification for only transmitting changed parts of the image. This means that currently, 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.

With a single DVI link, the largest resolution possible at 60Hz is 2.6 megapixels. The DVI connector therefore has provision for a second link, containing another set of red, green, and blue twisted pairs. When more bandwidth is required than is possible with a single link, the second link is enabled, and alternate pixels may be transmitted on each. The DVI specification mandates a fixed single link cutoff point of 165 MHz, where all display modes that require less than this must use single link mode, and all those that require more must switch to dual link mode. When both links are in use, the pixel rate on each may exceed 165 MHz. The second link can also be used when more than 24 bits per pixel is required, in which case it carries the least significant bits.

Read more at Wikipedia.org