High Definition Multimedia Interface (HDMI)
November 13, 2008
Two different media require an interface to transmit information between each other. Interfaces are mainly used to connect two different sources. Various connectors are now available and few to mention are interfaces to connect audio and video sources; electrical connectors to connect different electric circuits; network interfaces to connect a user terminal and public or private network; user interface that connects the user with the system; and physical interfaces that connects the hardware components. HDMI is one such interface that is used to connect digital audio and video sources.
What is HDMI?
HDMI (High Definition Multimedia Interface) is an audio and video connector interface that is mainly used to carry uncompressed digital streams. It connects various digital audio and video sources such as Blu-ray disc players, set-up boxes, video game consoles, personal computers to various other devices such as computer monitors, digital televisions and digital audio devices. This is a digital alternative to various standards like composite video, S-Video, component video, SCART, VGA and D-Terminal. HDMI supports any PC video format or TV that is either an enhanced model or a standard model on a single cable wire together with 8 channels of digital audio.
As many as 800 PC companies have accepted to adopt the HDMI specification. In the year 2006, HDMI first appeared in digital still camera and camcorders. It was produced and distributed in the year 2003. Though HDMI devices are produced according to the different specifications, each version uses the same kind of cable that have different capabilities and also increased bandwidth.
HDMI supports audio streams like DTS (Digital Theatre System) and Dolby digital and uncompressed digital audio(8 channel) at a sample rate of 192KHz. About 8 channels that consist of one bit DSD (Direct Stream Digital) audio are supported by this HDMI. It also supports producers of motion pictures such as Universal, Warner Bros., Fox and Disney. Some of the founders of HDMI are Philips, Silicon image, Hitachi, Toshiba, Thomson and Matsushita electric Industrial.
Various specification of HDMI are signals, protocols, mechanical requirement and electrical interfaces. Different versions of HDMI devices are HDMI 1.0, HDMI 1.1, HDMI 1.2, HDMI 1.2a, HDMI 1.3, HDMI 1.3a, HDMI 1.3b, HDMI 1.3b1 and HDMI 1.3c.
History
AV connectors that is compatible to DVI (Digital Visual Interface) was the basic idea behind the production of HDMI that started in the year 2002. During those times DVI-HDTV and DVI-HDCP (High-bandwidth Digital Content Protection) were applied on HDTV(High Definition Television). About 5 million HDMI devices were sold in the year 2004 according to In-Stat.
Connectors
The three connectors of the HDMI connector are Type A and Type B for HDMI 1.0 specification and Type 3 for HDMI 1.3 specification. Type A connector comes with 19 pins that has bandwidths to support SDTV, HDTV and EDTV. Type B connector comes with 29 pins that can carry double video bandwidth(Type A). Type C is designed mostly for portable devices and comes with 19 pins configuration but smaller than Type A connector. You can easily connect Type C connector to the Type A with the Type A to Type C connector cable. HDMI cables are designed to carry audio, video and device controlling signals.
To remove confusion about different cables supporting different video formats, HDMI cables have been defined in two categories. Cables that come under Category 1 is tested at 74.5MHz and cables that come under Category 2 is tested at 340MHz. According to the HDMI website, HDMI cables that were developed before HDMI 1.3 specification measures less than 5 meters that can be operated as the Category 2 cable (Category 2 tested cables are only to be used). Cables that are very long cause disturbances and instability because of weak signals. HDMI cables that work with electronics increase the signal strength that are about 30 meters.
HDMI is thus used as an audio and video connector to transmit uncompressed digital streams. Interfaces are thus helpful when two media are totally different.
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