HDMI

(CC) Photo: Alexey Goral
HDMI connector.

HDMI is a type of audio-visual digital cable as well as an emerging standard for digital transmission. HDMI stands for High-Definition Multimedia Interface and is a format shared by a wide variety of electronic devices. It emerged in the middle of the 2000s and is becoming increasingly accepted. HDMI promises to make cabling simpler yet robust. HDMI enables digital devices to send signals to computer monitors and digital televisions including HDTV. Devices such as a DVD player, set-top box, audio video receiver, Blu-ray disc player, personal computers, video game consoles and such can send signals to each other if they are HDMI equipped. According to a marketing promotion, HDMI is the "de facto standard digital interface for high definition TV and the consumer electronics market." However, consumers buying new HDTVs find they need to buy HDMI cables, and many cables are sold at rates which some electronics experts believe are exhorbitant. One benefit of the HDMI cable is that it helps cut the clutter of too many wires since both audio and video signals are sent along the same cable. In consumer parlance, HDMI is often thought of as a cable, but to electronics firms, it's thought of as a digital transmission standard.

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The HDMI, which stands for high-definition multimedia interface, is used to transfer digital sound and video signals from various devices to the TV without degrading those signals.

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HDMI cables typically replace an earlier standard that never caught on called "DVI", a standard introduced around 2005, and some TVs don't even have DVI ports. Generally, cables work best when there is a short distance between the source and the TV, such as six feet or less; but there are solutions to wiring up a whole house which involve special cables or what are called "extenders", or connecting up devices to an Ethernet system. Cables should be handled gently and not pulled through walls without proper tools to keep them from breaking.

Ports behind the new HDTVs

The backs of the new HDTV are awash with ports from "connectors of the past" which can make hooking up wires an exercise in head scratching. According to one report, new HDTVs often have three HDMI ports, sometimes as many as five, since there are many devices which will try to be played through a TV, including a personal computer as well as game consoles such as a Sony Playstation 3 or Microsoft Xbox. Manufacturers of HDTVs pay a licensing fee for each HDMI port that is added to the back of a television. Some makers are putting HDMI ports to the sides of the TVs to make installation easier. If a TV only has one HDMI port but there are many devices wanting to hook up to it, each with HDMI cables, it's possible to buy an "AV receiver", sometimes marketed as a "home theater in a box." These have numerous ports. A less expensive solution is to buy a "multiport switch box", which allows numerous incoming HDMI cables, and outputs one HDMI cable that runs to the television; by using a remote control, a user can choose which device gets played through the TV. Regardless, with the many options, a New York Times reporter suggested the back area of a new HDTV can look like a "snake pit of cables."

Consumer reaction to expensive cables

Buyers of new HDTVs will often have to purchase the HDMI cable in addition; cables mostly do not come with the TVs. HDMI cables can cost around $50 or more per cable. A four foot cable from one manufacturer costs $90.

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And when you walk over to the cable aisle at your electronics store, be ready for sticker shock — a four-foot shank of HDMI cable can cost $150. Some can be found for as little as $20, but some store sales representatives are quick to tell you that the expensive cable provides better picture quality than cheaper cables. They say that, in part, because the profit margin on the cables is higher than on many TVs they sell.

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Different HDMI cable makers include Monster, Belkin, Dynex, Susteen DataPilot, and Apple AirPort Express. The Monster 1000HD cable costs from $95 to $130.

But some product researchers suggest that there's little difference between a $10 HDMI cable and a $100 one. One reviewer from CNET termed the high cable prices a "rip off." A technology reporter said the cable doesn't contribute to the quality of the picture but merely moves it from "one place to the other" and advised against spending too much for HDMI cables. Reviewers from Consumer Reports, How Stuff Works, Popular Mechanics and CNET who have tested different cables, agree that "you can expect flawless performance from any 4-meter cable, regardless of price." Why do stores charge so much for the cables? A reporter from the Christian Science Monitor wrote:

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The secret is that stores don’t make much profit off TVs and video-game consoles. So to balance out the big items, most retailers mark up the little things. For example, the retail watchdog Con­sumerist.com published a 2008 wholesale list from Monster Cables, the high-end brand that hawks some of the most expensive cords. The suggested retail price for its four-foot HDMI cable is $79.99. But it wholesales for $38.23 – less than half the sticker price.

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A spokesperson for cable maker Monster responded that its cables were "built to withstand wear and tear" with improved insulation and connectors, and that its cables were "somewhat futureproof."

Cables for different uses

According to an HDMI web site, there are five different types of HDMI cables (after the 1.4 specification) which have different uses. Data along each of the types of cables is sent uncompressed. The new HDMI 1.4 cable enables users to send broadband data from a TV to a video game console, which eliminates a need for an Ethernet cable between the two devices. The new standard includes an "audio return channel" which enables audio fed to a TV to be forwarded to an external receiver and turned into 5.1 channel surround sound. This means that there's no need to run audio cables to a receiver and to a TV.

• Standard HDMI Cable is designed for most home uses and can reliably transmit 1080i or 720p video, which are the common types with HDTVs. This is the cable that most HDTVs will need.

• Standard HDMI Cable with Ethernet offers some baseline performance plus has an additional dedicated data channel known as the HDMI Ethernet. It helps devices network with each other. It works when both linked devices are "HDMI Ethernet Channel-enabled", according to HDMI.

• Automotive Standard Automotive is designed for internal cabling within vehicles with onboard HD video systems. The cables are marketed as being "capable of withstanding the unique stresses of the motoring environment such as vibration and temperature extremes."

• HDMI High Speed is designed for video resolutions of 1080p and beyond, including advanced display technologies such as 4K, 3D, and Deep Color. If using these technologies or connecting an 1080p display to a 1080p content source, such as a Blu-ray Disc player, this is the recommended cable.

• HDMI High Speed with ETHERNET is like the HDMI High Speed (1080p and beyond), plus it has an additional dedicated data channel known as the HDMI Ethernet Channel for device networking. (HDMI Ethernet Channel functionality is only available if both linked devices are HDMI Ethernet Channel-enabled.)

Cable handling

One guideline from the HDMI web site recommends gentle handling of the cables:

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Remember how much data is running through that cable and treat it with a light touch. Tolerances are tight, so be careful - don’t yank HDMI cables or twist connectors. For in-wall installations, pull-through socks are available that will protect the connector as the cable is pulled through the wall or conduit. This is a particularly good idea if you are installing an active cable, where the connectors are larger and more sensitive because of their embedded electronics.

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Most HDMI connectors are called "Type A" Standard but some new portable devices such as HD videocameras and digital still cameras are using the "Mini-Connector" called "Type C". Adapters are available.

Short six-foot cables work best

When the distance between the source and the receiver begins to get too long, such as over ten feet, then longer cable lengths raise the chance that the signal may become degraded. One way to solve this is by using an HDMI extender. It's a single device (or pair of devices) powered with an external power source or with the 5V DC from the HDMI source. Long cable lengths can cause instability of HDCP and blinking on the screen, due to the weakened Display Data Channel (DDC) signal that HDCP requires. HDCP DDC signals must be multiplexed with TMDS video signals to be compliant with HDCP requirements for HDMI extenders based on a single Category 5/Category 6 cable. Several companies offer amplifiers, equalizers, and repeaters that can string several standard HDMI cables together. Active HDMI cables use electronics within the cable to boost the signal and allow for HDMI cables of up to 30 meters (98 ft.). HDMI extenders that are based on dual Category 5/Category 6 cable can extend HDMI to 250 meters (820 ft.), while HDMI extenders based on optical fiber can extend HDMI to 300 meters (980 ft.).

Encrypted HDMI

HDMI can use High-bandwidth Digital Content Protection, or HDCP to encrypt the signal if required by the source device. Content Scramble System, Content Protection for Recordable Media, and Advanced Access Content System require the use of HDCP on HDMI when playing back encrypted DVD Video, DVD Audio, HD DVD and Blu-ray Disc. The HDCP Repeater bit controls the authentication and switching/distribution of an HDMI signal.

History

HDMI products began appearing in autumn 2003. Several sources claim over 850 consumer electronics and computer firms have adopted the HDMI specification. In Europe, either DVI-HDCP or HDMI is included in the HD ready in-store labelling specification for TV sets for HDTV, formulated by the European Information, Communications and Consumer Electronics Technology Industry Associations with SES Astra in 2005. HDMI began to appear on HDTV camcorders and digital cameras in 2006. Shipments of HDMI were expected to exceed that of DVI in 2008, driven primarily by the consumer electronics market.

The HDMI Founders are Hitachi, Matsushita Electric Industrial, Philips, Silicon Image, Sony, Thomson (RCA), and Toshiba. Digital Content Protection, LLC provides HDCP (which was developed by Intel) for HDMI. HDMI has the support of motion picture producers 20th century Fox, Universal Studios,[Warner Bros., and Disney, along with system operators DirecTV, EchoStar, and CableLabs.