HDMI/DVI Hassles, Continued – With many more people bringing digital video gear of various sorts into their homes this season, incidences of connections failing are on the rise. One expert flatly stated, “Many devices have issues when going from HDMI to DVI or reverse.” First, with tips from the Ram Electronics Industries site, here are the basics: DVI stands for Digital Visual Interface; HDMI stands for High Definition Multimedia Interface. Both are being used in displays, HDTVs, video projectors, DVD players, cable/satellite set-top boxes and associated gear. The idea is to provide a superior digital image – as the component analog video connection does over S-video and composite connections – plus where applicable, also including the digital audio connections in the same cable. HDMI and DVI were adopted by the AV industry because of the overriding concern of both movie studios and music companies about copyright protection of their products.
This brings up more acronyms: DRM (Digital Rights Management) is the overall effort to control copying of music and movies. HDMI and DVI got industry approval because they are compliant with HDCP (High-Bandwidth Digital Content Protection). HDCP allows the user of a program or disc to either make, say, just one copy for personal use or no copy at all. It may allow it to play only on certain equipment or to be blocked after a certain length of time. The constraints of HDCP are usually behind problems that come up. HDMI is in a continual version upgrade (the latest carries more channels of digital audio) and each new version seems to be capable of causing different bugs in certain applications. Being digital, the problems are completely different from those with analog cables. And cables, of all AV components, are possibly the most vulnerable to “Murphy’s Law.”
There are three parts to a DVI or HDMI system and they are interdependent on one another for an AV signal to be transmitted properly: 1. The solid state board in the component must transmit the signal properly; 2. The cable itself must carry the signal with the lowest possible jitter, skew, crosstalk and attenuation. Cables over 15 ft. or so can cause problems; 3. The receiver end must be capable of recovering the incoming data signal and verifying the HDCP portion of it. Specs are normally not published for such cables. Ram Electronics recommends a single high quality DVI/HDMI cable connected directly to the equipment and with the shortest possible run. They suggest working with a dealer who will allow you to test the cable with your gear and then simply using what works. DVI does not pass audio signals and earlier HDMI only passes two channel audio, so you may be using a coaxial audio connection or a six-channel analog array in addition to the digital video cable.
