High-Definition Multimedia Interface
From Free net encyclopedia
Image:High Definition Multimedia Interface Plug.jpg
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 DTV 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 artificially downgraded by the signal source to prevent the end user from viewing or especially copying restricted content. Type B HDMI is similarly backward-compatible with dual-link DVI.
The HDMI Founders include 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.
Contents |
Technical specifications
TMDS channel
- Carries audio, video and auxiliary data.
- Signalling method: According to DVI 1.0 spec. 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 25 MHz (e.g. 13.5 MHz for 480i/NTSC) transmitted using a pixel-repetition scheme. Up to 24 bits per pixel can be transferred, regardless of rate. Supports 1080p60[1].
- Pixel encodings: RGB 4:4:4, YCbCr 4:4:4 (8 bits per component); YCbCr 4:2:2 (12 bits per component)
- 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 sinc.
- 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.
Cost
Consumer grade HDMI adapters and cables may be found at a wide range of price points. $10 on eBay (including shipping), $45 at discount retailers such as Wal-Mart, and $40 - $300 at electronics retailers such as Circuit City and Best Buy.
As HDMI transmits sound and video digitally (similar to USB and FireWire), any cable that meets the minimum standard will work correctly. However, some manufacturers erroneously claim that better cables provide a better picture quality, by means of improvements such as better shielding to block more RFI and EMI, nitrogen foam dielectric to keep a constant 100 ohm impedance, gold tips for corrosion-free connections, and silver-plated copper for the best conductors possible.
The one situation where more expensive cables may help is with very long cables, the digital transfer will typically work perfectly until some value (noise, attenuation etc) goes past a threshold. Beyond this point the number of bit errors induced by the cable will increase very rapidly. A "better" cable may push this threshold far enough away for the error rate to fall back into the normal (very low) range.
Content Protection
- According to High-Definition Content Protection (HDCP) Specification 1.10.
Connector detail
Connector example: Molex 500254-1907
| 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 | +5 V Power |
| 19 | Hot Plug Detect |
See also
External links
- Consumer FAQ
- Official HDMI Website
- HDMI Switches
- All About HDMIaf:High-Definition Multimedia Interface
cs:HDMI de:High Definition Multimedia Interface es:High-Definition Multimedia Interface fr:High-Definition Multimedia Interface ko:HDMI it:HDMI nl:High-Definition Multimedia Interface ja:HDMI pl:Hdmi ru:HDMI fi:HDMI sv:HDMI