HDMI (High-Definition Multimedia Interface) is a compact audio/video interface for transmitting uncompressed digital data. It represents a digital alternative to consumer analog standards, such as radio frequency (RF) coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA. HDMI connects digital audio/video sources—such as set-top boxes, upconvert DVD players, HD DVD players, Blu-ray Disc players, AVCHD camcorders, personal computers (PCs), video game consoles such as the PlayStation 3, Xbox 360, and AV receivers—to compatible digital audio devices, computer monitors, and digital televisions.
HDMI products started shipping in late 2003. Over 850 consumer electronics and PC companies have adopted the HDMI specification (HDMI Adopters). In Europe, either DVI-HDCP or HDMI is included in the HD ready in-store labeling specification for TV sets for HDTV, formulated by EICTA with SES Astra in 2005. HDMI began to appear on consumer HDTV camcorders and digital still cameras in 2006. Shipments of HDMI were expected to exceed that of DVI in 2008, driven primarily by the consumer electronics market.
Although no maximum length for a HDMI cable is specified, signal attenuation—dependent on the cable's construction quality and conducting materials—limits usable lengths in practice. HDMI 1.4 defines two cable categories: Category 1-certified cables, which have been tested at 74.25 MHz (which would include resolutions such as 720p60 and 1080i60), and Category 2-certified cables, which have been tested at 340 MHz (which would include resolutions such as 1080p60 and 2160p30). Category 1 HDMI cables are to be marketed as "Standard" and Category 2 HDMI cables as "High Speed". This labeling guideline for HDMI cables went into effect on October 17, 2008. Category 1 and 2 cables can either meet the required parameter specifications for interpair skew, far-end crosstalk, attenuation, and differential impedance, or they can meet the required nonequalized/equalized eye diagram requirements. A cable of about 5 meters (16 ft.) can be manufactured to Category 1 specifications easily and inexpensively by using 28 AWG (0.081 mm2) conductors. With better quality construction and materials, including 24 AWG (0.205 mm2) conductors, a HDMI cable can reach lengths of up to 15 meters (49 ft.). Many HDMI cables under 5 meters of length that were made before the HDMI 1.3 specification can work as Category 2 cables, but only Category 2-tested cables are guaranteed to work.