High-Definition Multimedia Interface

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The High-Definition Multi-media Interface (HDMI) is an industry-supported, uncompressed, all-digital audio/video interface. HDMI provides an interface between any compatible digital audio/video source, such as a set-top box, DVD player, and A/V receiver and a compatible digital audio and/or video monitor, such as a digital television (DTV).

HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It is independent of the various HDTV standards such as ATSC, DVB(-T,-S,-C), as these are encapsulations of the MPEG data streams, which are passed off to a decoder, and output as uncompressed high-resolution video data. This video data is then encoded into TMDS for transmission digitally over HDMI. HDMI also includes 8-channel digital audio.

The standard Type A HDMI connector has 19 pins, and a higher resolution version called Type B, has been defined, although it is not yet in common use. Type B has 29 pins, allowing it to carry an expanded video channel for use with high-resolution displays. Type-B is designed to support resolutions higher than 1080i and thus is not yet necessary.

Type A HDMI is backwards-compatible with the single-link Digital Visual Interface (DVI) used on modern computer monitors and graphics cards. This means that a DVI source can drive an HDMI monitor, or vice versa, by means of a suitable adapter or cable, but the audio and remote control features of HDMI will not be available. Additionally, without support for HDCP, the video quality and resolution may be downgraded by the player unit. Type B HDMI is similarly backwards-compatible with dual-link DVI.

The HDMI Founders include leading consumer electronics manufacturers Hitachi, Matsushita Electric Industrial (Panasonic), Philips, Sony, Thomson (RCA), Toshiba, and Silicon Image. Digital Content Protection, LLC (a subsidiary of Intel) is providing High-bandwidth Digital Content Protection (HDCP) for HDMI. In addition, HDMI has the support of major motion picture producers Fox, Universal, Warner Bros. and Disney, and system operators DirecTV, EchoStar (Dish Network) as well as CableLabs.


Technical Specifications

TMDS channel

  • Carries audio, video and auxiliary data.
  • Signalling method: According to DVI 1.0 specification. Single-link (Type A HDMI) or dual-link (Type B HDMI).
  • Video pixel rate: 25 MHz to 165 MHz (Type A) or to 330 MHz (Type B).
  • Pixel encodings: RGB 4:4:4, YCbCr 4:2:2, YCbCr 4:4:4.
  • Audio sample rates: 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96kHz, 176.4 kHz, 192 kHz.
  • Audio channels: up to 8.

DDC channel

  • Allows source to interrogate capabilities of sink.
  • I²C signalling with 100 kHz clock.
  • E-EDID data structure according to EIA/CEA-861B and VESA Enhanced EDID.

Consumer Electronics Control (CEC) channel (optional)

  • Uses the industry standard AV Link protocol
  • Used for remote control functions.
  • One-wire bidirectional serial bus.
  • Defined in HDMI Specification 1.0.

Content Protection

  • According to High-Definition Content Protection (HDCP) Specification 1.10.

Connector Detail

Connector example: Molex 500254-1907

Type A Connector Pin Assignment

PinSignal AssignmentPinSignal Assignment
1TMDS Data2+2TMDS Data2 Shield
3TMDS Data2–4TMDS Data1+
5TMDS Data1 Shield6TMDS Data1–
7TMDS Data0+8TMDS Data0 Shield
9TMDS Data0–10TMDS Clock+
11TMDS Clock Shield12TMDS Clock–
13CEC14Reserved (N.C. on device)
17DDC/CEC Ground18+5V Power
19Hot Plug Detect

Web site

See also

Digital Visual Interface (DVI)af:High-Definition Multimedia Interface de:High Definition Multimedia Interface ja:HDMI


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