KVM

The High-Definition Multimedia Interface ^® (HDMI) is the first digital interface to combine uncompressed high-definition video, up to eight channels of uncompressed digital audio, and intelligent format and command data in a single cable. It is now the defacto standard for consumer electronics and high-definition video and is gaining ground in the PC world.

HDMI supports standard, enhanced, and high-definition video. It can carry video signals at resolutions up to and beyond 1080p at 60 Hz (and higher).

HDMI offers an easy, standardized way to set up home theaters and AV equipment over one cable. Use it to connect audio/video equipment, such as DVD players, a set-top box, and A/V receivers with an audio and/or video equipment, such as a digital TV, PCs, cameras, and camcorders. It also supports multiple audio formats from standard stereo to multichannel surround sound. Plus it provides two-way communications between the video source and the digital TV, enabling simple, remote, point-and-click configurations.

NOTE: HDMI also supports HDCP (High-bandwidth Digital Content Protection), which prevents the copying of digital audio and video content transmitted over HDMI cable. If you have a device between the source and the display that supports HDMI but not HDCP, your transmission won’t work, even over an HDMI cable.

HDMI offers significant benefits over older analog A/V connections. It’s backward compatible with DVI equipment, such as PCs, TVs, and other electronic devices using the DVI standard. A DVI-to-HDMI adapter can be used without a loss of video quality. Because DVI only supports video signals, not audio, the DVI device simply ignores the extra audio data.

HDMI standards
The HDMI standard was introduced in December 2002. Since then, there have been a number of versions with increasing bandwidth and/or transmission capabilities.

HDMI 1.0 has a maximum TMDS bandwidth of 4.9 Gbps. It supports up to 3.96 Gbps of video bandwidth (1080p/60 Hz or UXGA) and 8-channel LPCM/192-kHz/24-bit audio.

HDMI 1.1 (May 2004) added support for full-definition DVD audio.

HDMI 1.2 (August 2005) added support for one-bit audio for SACD (Super Audio CD).

HDMI 1.2a (December 2005) added Consumer Electronics Controls (CEC) capabilities, such as command sets for controlling multiple devices with a single remote.

HDMI 1.3 (June 2006), more than doubled the bandwidth from 4.95 Gbps to 10.2 Gbps (340 MHz). It offers support for 16-bit color, increased refresh rates, and added support for 1440p WQXGA. It also added support for xvYCC color space and Dolby True HD and DTS-HD Master Audio standards. Plus it added features to automatically correct audio video synchronization. Finally, it added a mini connector.

HDMI 1.3a (November 2006), HDMI 1.3b (March 2007), HDMI 1.3b1 (November 2007), and 1.3c (August 2008) added termination recommendations, control commands, and other specification for testing, etc.

HDMI 1.4 (May 2009) increased the maximum resolution to 4Kx 2K (3840 x 2160 p/24/25/30 Hz and 4096 x 2160/24 Hz). It added an HDMI Ethernet channel for a 100-Mbps connection between two HDMI devices. Other advancements include: an Audio Return Channel, stereoscopic 3D over HDMI (HDMI 1.3 devices will only support this for 1080i), an automotive connection system, and the micro HDMI connector.

HDMI 1.4a (March 2010) adds two additional 3D formats for broadcast content.

HDMI connectors
There are four HDMI connector types. Type A and Type B are defined in the HDMI 1.0 specification. Type C is defined in HDMI 1.3, and Type D is defined in HDMI 1.4.

Type A: 19 pins. It supports all SDTV, EDTV, and HDTV modes. It is electrically compatible with single-link DVI-D.

Type B: 29 pins. Offers double the video bandwidth of Type A. Use for very high-resolution displays such as WQUXGA. It’s electrically compatible with dual-link DVI-D.

Type C Mini: 19 pins. This mini connector is intended for portable devices. It is smaller than Type A but has the same pin configuration and can be connected to Type A cable via an adapter or adapter cable.

Type D Micro: 19 pins. This also has the 19-pin configuration of Type A but is about the size of a micro-USB connector.

HDMI cable
Recently, HDMI Licensing, LLC announced that cables would be tested as Standard or High-Speed cables.

Standard HDMI cable is designed for use with digital broadcast TV, cable TV, satellite TV, Blu-ray and upscale DVD players to reliably transmit up to 1080i or 720p video (or the equivalent of 75 MHz or up to 2.25 Gbps).

High-Speed HDMI reliably transmits video resolutions of 1080p and beyond, including advanced display technologies such as 4K, 3D, and Deep Color. High-Speed cables can also accommodate WQXGA cinema monitors (resolution of 2560 x 1600). High-Speed HDMI is the recommended cable for 1080p video. It will perform at speeds of 340 MHz or up to 10.2 Gbps, the highest bandwidth currently available over an HDMI cable.

Additional resources and licensing information is available at HDMI.org.

The ABCs of standards
There are two primary organizations dedicated to developing and setting structured cabling standards. In North America, standards are issued by the Telecommunications Industry Association (TIA), which is accredited by the American National Standards Institute (ANSI). The TIA was formed in April 1988 after a merger with the Electronics Industry Association (EIA). That’s why its standards are commonly known as ANSI/TIA/EIA, TIA/EIA, or TIA.

Globally, the organizations that issue standards are the International Electrotechnical Commission (IEC) and the International Organization for Standardization (ISO). Standards are often listed as ISO/IEC. Other organizations include the Canadian Standards Association (CSA), CENELEC (European Committee for Electrotechnical Standardizations), and the Japanese Standards Association (JSA/JSI).

The committees of all these organizations work together and the performance requirements of the standards are very similar. But there is some confusion in terminology.

The TIA cabling components (cables, connecting hardware, and patch cords) are labeled with a ”category.” These components together form a permanent link or channel that is also called a ”category.” The ISO/IEC defines the link and channel requirements with a ”class” designation. But the components are called a ”category.”

The Standards
Category 5 (CAT5), ratified in 1991, was the de facto standard for 100-Mbps networks during the 1990s. It is no longer recognized by the TIA/EIA for use in data networking.

Category 5e (CAT5e)–ISO/IEC 11801 Class D, ratified in 1999, is designed to enable twisted-pair cabling to support full-duplex, 4-pair transmission in 100-MHz applications. The CAT5e standard added more headroom and established new requirements to support Gigabit Ethernet over a worst case four-connector channel. These include stricter specs for Near-End Crosstalk (NEXT) and Return Loss (RL). The standard also introduced the required measurements for Power Sum Near-End Crosstalk (PS-NEXT), Equal-Level Far-End Crosstalk (EL-FEXT), and Power Sum Equal-Level Far-End Crosstalk (PS-ELFEXT). CAT5e is still used in many organizations, although it is no longer recognized for new installations.

Category 6 (CAT6)–Class E has a specified frequency of 250 MHz, significantly improved bandwidth capacity over CAT5e, and easily handles Gigabit Ethernet transmissions. In recent years, it has been the cable of choice for new structured cabling systems. CAT6 supports 1000BASE-T and, depending on the installation, 10GBASE-T (10-GbE).

10-GbE over CAT6 introduces the problem of Alien Crosstalk (ANEXT), the unwanted coupling of signals between adjacent pairs and cables. Because ANEXT in CAT6 10-GbE networks is so dependent on installation practices, TSB-155 qualifies 10-GbE over CAT6 up to 55 meters and requires it to be 100% tested. To mitigate ANEXT in CAT6, it is recommended that you unbundle the cables and increase the separation between the cables.

Augmented Category 6 (CAT6a)–Class Ea was ratified in February 2008. This standard calls for 10-Gigabit Ethernet data transmission over a 4-pair copper cabling system up to 100 meters. CAT6a extends CAT6 electrical specifications from 250 MHz to 500 MHz. It introduces the ANEXT requirement. It also replaces the term Equal Level Far-End Crosstalk (ELFEXT) with Attenuation to Crosstalk Ratio, Far-End (ACRF) to mesh with ISO terminology. CAT6a provides improved insertion loss over CAT6. It is a good choice for noisy environments with lots of EMI. CAT6a is also well-suited for use with PoE+.

CAT6a UTP cable is significantly larger than CAT6 cable. It features larger conductors, usually 22 AWG, and is designed with more space between the pairs to minimize ANEXT. The outside diameter of CAT6a cable averages 0.29–0.35" compared to 0.21–0.24" for CAT6 cable. This reduces number of cables you can fit in a conduit. At a 40% fill ratio, you can run three CAT6a cables in a 3/4" conduit vs. five CAT6 cables.

There are two types of CAT6a cable, UTP and F/UTP. For a discussion of the differences, see the white paper in our Resources section.

Category 7 (CAT7)–Class F was published in 2002 by the ISO/IEC. It is not a TIA recognized standard. Class 7 specifies minimum performance standards for fully shielded cable (individually shielded pairs surrounded by an overall shield) transmitting data at rates up to 600 MHz. It offers greater capacity for demanding applications such as broadband video. It’s also well suited for applications where fiber optic cable would typically be used—but it costs less. Because each CAT7 pair is fully shielded, it's ideal for areas prone to EMI/RFI. Class 7 cable offers two connector styles: the standard RJ plug and a non-RJ-style plug and socket interface specified in IEC 61076-2-104:2.

Category 7a (CAT7a)–Class Fa is currently in ISO standards for channel performance in Amendment 1, recently component performance has been ratified in Amendment 2. The formal names are ISO 11801 Amendment 1 (2008) and ISO 11801 Amendment 2 (2010). Class Fa cable is a fully shielded cable that extends frequency from 600 MHz to 1000 MHz. It can easily handle 10-GbE and offers users a lifespan of 15 years or more. It has even been discussed that Class Fa cable is the future for 40GBASE-T or more.


For a comparison chart of category performance standards, see the Buyer's Guide in the Resources section.