Media Theater Studio Xperience

DVI: For High Quality Digital Displays

The need for crystal clear display on visual devices led to the production of new technologies such as DVI. With DVI technology, producing high quality output for TV and projectors has become possible.

The brainchild of the Digital Display Working Group (DDWG) the DVI (digital video interface) has dramatically altered the image quality of display devices, from LCDs to computer monitors to projectors.

The Need for DVI

Before DVI, the standard used was the Video Graphics Array (VGA), and was intended for the use on CRT monitors. The basic process involved a source that emits horizontal lines of the image, at the same time it changes the output voltage according to certain brightness levels.

The CRT, which receives this transmission, changes the electron beam while scanning the display monitor.

This approach could not work with digital displays, because every pixel there had to be sampled to get an accurate display.

How DVI Works

With the Digital Video Interface, distortion no longer presented a problem. Instead of just adjusting the output voltage to determine brightness, DVI takes the brightness of every pixel and puts in a binary code.

Using this method, all the pixels in the source will match correctly with those in the display. This allows for a noise and distortion free screen.

The Technology of DVI

The DVI utilizes a format based on the Pnnel Serial which makes use of the Transition Minimized Differential Signaling (TMDS).
All the wires in a DVI (colored red, green and blue and one a clock signal) transmit 24 bits for every pixel. With intervals, the picture images are sent line by line without any form packets. Another advantage of DVI is that it does not use any compression, which was a problem that affected older technologies.

DVI Links

One DVI link can support a maximum resolution of 2.6 megapixels at 60Hz, but it has the capability to use other links if the resolution is going to be much higher. Thus there are two modes, the single link, for those displays that require less than 2.6 megapixels, and dual link mode, for that need more megapixels. The dual link mode is also sued when more than 24 pixel bits are needed.

DVI Connectors

Unlike LDVS and Open LDI, DVI provides support for digital and analog transmissions. The DVI connectors are thus classified into the following: DVI-A (DVI Analog), DVI-I (DVI Digital and Analog) and DVI-D (DVI Digital). The DVI-D can, in some instances, work with HDMI (High definition Multimedia Interface).

DVI Specifications

The minimum clock frequency for DVI is 25.175Mhz, and its maximum has been set to 165Mhz. In dual link mode however, the limit is set only by the cable. The pixels per clock cycle for single mode is 1, and for dual link 2. The bits per pixel is set at 24 while in dual mode it is 48.

DVI Display Modes

For single link, the following displays are possible:
HDTV (1920 × 1080) (60Mhz); UXGA (1600 × 1200) (60Mhz); SXGA (1280 × 1024) (159 MHz); WXGA+ (1440 x 900) (107 MHz) and WQUXGA (3840 × 2400) (164 MHz)

For dual links:

QXGA (2048 × 1536) (2×170 MHz); HDTV (1920 × 1080) (2×126 MHz); WQXGA (2560 × 1600) (2x174 MHz); WQXGA (2560 × 1600) (2x135 MHz) and (WQUXGA (3840 × 2400) (2x159 MHz)

About the Author:
Peter Garant is writing articles about DVI HDTV Connectors for a site about DVI.