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, and VGA. HDMI connects digital audio/video sources such as set-top boxes, Blu-ray Disc players, personal computers (PCs), video game consoles (such as the PlayStation 3 and Xbox 360), and AV receivers to compatible digital audio devices, computer monitors, and digital televisions.

HDMI supports, on a single cable, any TV or PC video format, including standard, enhanced, and high-definition video, up to 8 channels of digital audio, and a Consumer Electronics Control]] (CEC) connection. The CEC allows HDMI devices to control each other when necessary, and allows the user to operate multiple devices with one [[remote control handset. Because HDMI is electrically compatible with the signals used by Digital Visual Interface (DVI), no signal conversion needs to take place nor is there a loss of video quality when a DVI to HDMI adapter is used. As an uncompressed connection, HDMI is independent of the various digital television standards used by individual devices such as ATSC and DVB as these are encapsulations of compressed MPEG video streams (which can be decoded and output as an uncompressed video stream on HDMI).

HDMI products started shipping in autumn 2003. Over 850 Consumer Electronics (CE) 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 labelling 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 are expected to exceed that of DVI in 2008, driven primarily by the CE market.

Overview

HDMI supports, on a single cable, any TV or PC video format, including standard, enhanced, and high-definition video, up to 8 channels of digital audio, and the Consumer Electronics Control signal. HDMI encodes the video data into TMDS for uncompressed digital transmission over HDMI.

HDMI devices are manufactured to adhere to various versions of the specification, where each version is given a number such as 1.0, 1.2, or 1.3a. Each subsequent version of the specification uses the same kind of cable but increases the bandwidth and/or capabilities of what can be transmitted over the cable. For example the previous maximum pixel clock rate HDMI interface was 165 MHz which was sufficient for supporting 1080p at 60 Hz and WUXGA (1920×1200) at 60 Hz. HDMI 1.3 increased that to 340 MHz which allows for higher resolution, such as WQXGA (2560x1600), across a single digital link. A HDMI connection can either be single link (Type A/C) or dual link (Type B) and can have a video pixel rate of 25 MHz to 340 MHz for a single link connection or 25 MHz to 680 MHz for a dual link connection. Video formats with rates below 25 MHz (e.g., 13.5 MHz for 480i/NTSC) are transmitted using a pixel-repetition scheme.