HDMI® (High-Definition Multimedia Interface) is an interface standard used for audiovisual equipment, such as high-definition television and home theater systems. With 19 wires wrapped in a single cable that resembles a USB wire, the cable is able to carry a bandwidth of 5 gigabits per second (Gbps). This is more than twice the bandwidth needed to transmit multi-channel audio and video, future-proofing the interface for some time to come. This and several other factors make HDMI® much more desirable than its predecessors, component video, S-Video, and composite video.
Signals that travel through the HDMI® interface are uncompressed and all-digital, while the previous interfaces were all analog. With an analog interface, a clean digital source is translated into less precise analog, sent to the television, then converted back to a digital signal to display on screen. At each translation, the digital signal loses integrity, resulting in some distortion of picture quality. HDMI® preserves the source signal, eliminating analog conversion to deliver the sharpest, richest picture possible.
Previous video interfaces required separate audio cables, with the vast majority of people using standard RCA L/R analog audio jacks. HDMI®, with its abundant bandwidth and speed, carries not only video but also up to eight digital audio channels for uncompromised surround-sound. It replaces the tangle of wires behind the system with a single cable, greatly simplifying the entire setup process of the home theater system while delivering top tier performance.
Though standard HDMI® or "Type A" has 19 wires, "Type B" will have 29 wires. The latter is targeted for the motion picture industry and other professional applications. Both varieties are "Intelligent HDMI®," referring to the built-in capability for components to talk to each other via the interface. Auxiliary information can provide all-in-one remote functionality and other interoperable features not possible in previous interface technologies.
This interface supports standard video formats, enhanced video, and high-definition. It is also backward compatible with DVI (Digital Video Interface). High-end graphics cards featuring a DVI port can connect to the interface via a DVI/HDMI® cable. This is simply a cable with a DVI connector on one end and a HDMI® connector on the other. As a rule, cables should not run longer than 15 feet (5 meters), or degradation of the signal could occur.
Most modern television sets are sold with at least one HDMI® interface. Some experts advise that two interfaces will provide more flexibility, and for those who want to connect a game console, Blu-ray™ player, or other device, three might serve better. Multiple interfaces are likely become common on digital TVs as the industry incorporates this interface into more peripheral components.