Despite that in the home theater the digital video interface was soon superseded by HDMI Cable, yet it is still very much around. The problem for many is that the different types of DVI cables and connectors often represent nothing more but an incomprehensible interconnected mess.
Help is on the way! This short guide explains all there is the need to know about DVI interconnects.
The Digital Visual Interface, or DVI, was originally developed by the DDWG (Digital Display Working Group) in 1999.
It brought with it a number of different DVI cables and connectors to support the various signals that can be carried over a DVI interconnect.
However, it did not take long before this whole new mess of interconnects complicated itself even further. Soon, we saw the advent of a new digital interface that is closely related to DVI, the High Definition Multimedia Interface — or HDMI — and with it a whole new range of HDMI interconnects, HDMI to DVI cables, HDMI splitters, adaptors and HDMI connectors.
DVD players, digital cable and satellite set-top boxes, HDTVs, and home theater projectors, all represent prime targets for these digital connections. The new technology behind these connectors allows for direct digital connection between a digital source and the display device leaving you with pixel-for-pixel accurate images on your display. And though HDMI has become the de-facto standard in the high-definition video, DVI is still a very popular interface. By 2008, there were more than 100 million DVI-enabled devices around; and according to In-Stat.com, a marketing intelligence research group, shipment of DVI-enabled devices continued to increase till end-2011, following which shipments started declining by 9.4%; this annual decline rate is expected to continue till 2015.
This means that despite the dominant presence of HDMI, DVI-enabled devices are still very much present in both the home and the industry; coming across some DVI-enabled device is a reality that will remain with us for the years to come.
Digital Visual Interface Basics
The DVI connector can accommodate up to two TMDS (transition minimized differential signaling) links, the VESA Display Data Channel (DDC), the Extended Display Identification Data (EDID) services, as well as the red, green, blue and horizontal and vertical sync lines of an RGBHV analog video signal; the latter is included to safeguard backward compatibility with analog VESA video.
The use of TMDS means that DVI is fully compatible with both P&D and DFP (Digital Flat Panel) standards, and HDMI.
Each link in the DVI standard is made up of 3 data channels for RGB information and has a maximum bandwidth of 165MHz; this equates to 165 million pixels per second. Color support is up to 24-bit depth, with 8 bits per color. Each incoming 8-bit color data word is encoded by the DVI standard into a 10-bit transition minimized DC-balanced character, meaning that each pixel is represented by a total of 30-bits. This means that effective data throughput over a single link DVI cable is 4.95Gbps while in the case of dual link DVI, maximum data throughput is 9.9Gbps.
The only real major limitation of the DVI standard is the supported maximum cable length; this can be a serious hurdle to overcome in a dedicated home theater setup when connecting a DVI source with say a ceiling-mounted video projector.
This limitation arises out of the use of twisted-pair cable by the DVI Cables standard instead of coaxial cable to carry high bit-rate digital video, without employing any form of error correction. This can lead to severe problems with signal degradation over distance. At long cable lengths, cable quality becomes a critical factor that will affect the maximum supported bit-rate, and therefore signal resolution.