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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 digital television 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 video data, which can be high-definition. This video data is then encoded into TMDS for transmission digitally over HDMI. HDMI also includes support for 8-channel uncompressed digital audio. Beginning with version 1.2, HDMI now supports up to 8 channels of one-bit audio. One-bit audio is what is used on Super Audio CDs.

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 1080p.

Type A HDMI is backward-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 backward-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 and EchoStar (Dish Network) as well as CableLabs and Samsung.


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). Video formats with rates below 25MHz (e.g. 13.5MHz for 480i/NTSC) transmitted using a pixel-repetition scheme. Up to 24 bits per pixel can be transfered, regardless of rate.
  • 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
Pin Signal Assignment Pin Signal Assignment
1 TMDS Data2+ 2 TMDS Data2 Shield
3 TMDS Data2– 4 TMDS Data1+
5 TMDS Data1 Shield 6 TMDS Data1–
7 TMDS Data0+ 8 TMDS Data0 Shield
9 TMDS Data0– 10 TMDS Clock+
11 TMDS Clock Shield 12 TMDS Clock–
13 CEC 14 Reserved (N.C. on device)
15 SCL 16 SDA
17 DDC/CEC Ground 18 +5V Power
19 Hot Plug Detect

See also

External links

cs:HDMI de:High Definition Multimedia Interface fr:High-Definition Multimedia Interface it:HDMI nl:High-Definition Multimedia Interface ja:HDMI ru:HDMI fi:HDMI

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