High Definition Multimedia Interface (HDMI)

High Definition Multimedia Interface is one of the most used audio/video interface for transmitting uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compliant source device. These devices can be a display controller, a compatible computer monitor, video projector, digital television, or digital audio device. HDMI is a digital replacement for the standards of analog video.

HDMI implements the standards of EIA/CEA-861. This standard defines video formats and waveforms, transport of compressed and uncompressed LPCM audio, auxiliary data, and implementations of the VESA EDID. CEA-861 signals carried by HDMI are electrically compatible with the CEA-861 signals used by the digital visual interface (DVI). No signal conversion is necessary in HDMI. Also there is no loss of video quality when a DVI-to-HDMI adapter is used. The CEC (Consumer Electronics Control) capability allows HDMI devices to control each other when necessary. Also it allows the user to operate multiple devices with one handheld remote control device.

Several versions of HDMI have been deployed and developed since initial release of the technology, but all use the same cable and connector. Improvement in audio and video capacity, performance, resolution and color spaces came out with newer versions. Newer versions also have the optional advanced features such as 3D, Ethernet data connection, and CEC (Consumer Electronics Control) extensions.

Production of consumer HDMI products started in 2003. In Europe either DVI-HDCP or HDMI is included in the HD ready in-store labeling specification for HDTV which was formulated by EICTA with SES Astra in 2005. HDMI began to appear on consumer HDTVs in 2004. In camcorders and digital still cameras HDMI came in use in 2006.

Types of HDMI Cables:



  1. Standard cables –
    Also known as Category 1 HDMI cables perform at pixel speeds of 75 Mhz supporting bandwidth of about 2.23 Gbps. An uncompressed 1080i signal can be easily carried by them.

  2. High Speed cables –
    Also known as Category 2 HDMI cables perform at pixel speeds of 340 MHz supporting bandwidth of about 10.2 Gbps. The latest 1440p and WQXGA resolutions can be handled by them.

Advantages of using HDMI:

  • HDMI carries both the video and audio signal thus eliminating the need for separate audio cables.
  • HDMI enables many different connections with very few cables thus simplifying the connection process and eliminating the clutter of multiple cables.
  • Many new computers and laptops have an HDMI connection, which enables you to use this cable to turn your TV into a computer monitor.
  • With a special adapter, HDMI cables can convert to DVI thus providing additional connection options.

Disadvantages of HDMI:

  • Maximum distance for HDMI Cat1 cables is up to 35 meters for full capacity and is up to 10 meters for HDMI Cat2 cables. Beyond this limit extenders are needed.
  • Sometimes blank screens can be caused due to authentication delays called the switching delays. There can also be screen flashing errors.
  • There are limitations to field terminations of HDMI cables as they cannot be easily terminated in the field like their analog counterparts.
  • HDMI cables are more expensive than their analog counterparts.

Applications:

  1. Blu-ray Disc and HD DVD players
  2. Digital cameras and camcorders
  3. Personal computers
  4. Gaming consoles
  5. Tablet computers
  6. Mobile phones


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