High definition multimedia interface (HDMI®) is a connection system used with digital audio and video. An HDMI® cable is a specially designed cable capable of transmitting uncompressed digital video and audio simultaneously. This type of cable is used to connect digital input sources to digital televisions, receivers and computer monitors.
To view high definition video, Blu-Ray™ and eight channel digital audio, an HDMI® compliant TV, source and cable are required. An HDMI® cable is a replacement for two analog cables, video and sound. HDMI supports any TV or PC video format, ranging from standard to high definition.
The first HDMI® product was developed in 2002 to meet the requirements of a higher quality digital audio and visual system. The HDMI® specifications have been adopted by a wide range of computer, television and electronic manufacturers. These standards were developed by an association of consumer electronic manufacturing firms, in cooperation with major movie and music distribution companies.
There are two different types of HDMI® cable available for purchase, category one and two. The different categories only apply to HDMI® version 1.3 and above, which became available in October 2008. These cables are also backward compatible to earlier versions of HDMI®.
Category one HDMI® cables are labeled as standard cable and are ideal for transmitting 720p or 1080i audio and video signals. Category two cables are also called high speed HDMI® cable, and are able to carry 720p, 1080i and 1600p audio and video signals. Only category two cables are guaranteed to perform with a cable length greater than 16 feet (4.8 meters).
When selecting an HDMI® cable, cable length is an important consideration. Due to signal attenuation, there is a limit to the length of an HDMI® cable before performance is affected. If the cable is too long, the digital signal becomes too weak and the images on the screen blink.
The issues surrounding loss of signal due to excess cable length can be resolved through the use of HDMI® extenders, repeaters or equalizers. All these devices can be used to connect HDMI® cables to each other. With the use of these connecting devices, the cable length can extended without any loss of signal strength.
The maximum length possible depends on the category of cable used. Category five and six cables are able to increase the total cable length up to 164 feet (50 meters). If an optical fiber based HDMI® extender is used, the total cable length possible increases to 328 feet (100 meters).