As AV (audio-visual) and multimedia systems moved from analogue to digital, the demands placed on equipment called for a new interface to transfer digital data between devices and replace the myriad of leads developed over decades to connect various devices.
The digital interface of choice that has emerged as the de facto standard in the last 10 years is HDMI. It was developed following an initiative launched in early 2002 by the "HDMI Founders", a group of seven leading AV and connecting device manufacturers.
Ten years later, HDMI interfaces are found on virtually all new AV and multimedia devices such as TVs, home entertainment systems, PCs (personal computers), digital video cameras, tablet computers, game consoles and portable handheld devices. They are now also entering the automotive sector.
All in one, one for all
HDMI is typically used to connect a digital source, such as an HD DVD or a STB (set-top box) to an HDTV. A single HDMI cable combines video and multichannel audio. Using analogue leads, provision of the same connection would require three component video cables, plus six audio cables…
Because HDMI is a digital interface, it can deliver the clearest image of any cable type and handle HD video in the current 1080p (1 920 pixels wide by 1 080 high, progressive scan) format. It is the only connection that can carry 3D video signals.
HDMI can also support eight audio channels of the highest quality. Eight separate analogue cables would be needed to deliver audio of similar quality.
HDMI is compliant with a number of IEC International Standards, such as IEC 61937, Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958, for compressed audio streams, and also uses colour spaces defined in IEC 61966-2-4 Multimedia systems and equipment - Colour measurement and management – Part 2-4: Colour management – Extended-gamut YCC colour space for video applications – xvYCC, among others.
IEC TA (Technical Area) 1, Terminals for audio, video and data services and contents, part of TC (Technical Committee) 100: Audio, video and multimedia systems and equipment, includes HDMI in its specifications for DTT (Digital Terrestrial TV) and satellite and terrestrial receivers for ISDB (Integrated Services Digital Broadcasting).
Flexible and evolving interface
AV and multimedia equipment are constantly changing with new technologies and formats being continuously introduced. HDMI has been designed to ensure that new devices can be interconnected and improved standards supported.
This approach is similar to that adopted for the USB (Universal Serial Bus) standard used in computers and telecommunication devices. The current USB 3.0 is backward compatible and offers transfer rates up to 400 times faster than the original USB 1.0 (see article on USB in e-tech,November 2011).
HDMI 1.4b is now available. In addition to delivering a bandwidth and transfer rate twice those of the original HDMI 1.0 specifications, this version supports 4K TV (up to 16 times the current HDTV definition). It also offers an audio return channel that enables a TV to send audio data “upstream” to an AV receiver or surround sound controller, increasing user flexibility and eliminating the need for any separate audio connection. In addition, HDMI 1.4b provides an Ethernet channel that allows Internet-capable HDMI devices to be interconnected.
Up to 10 HDMI-enabled and connected devices, such as Blu-ray disc players or home entertainment systems, can be managed from a single remote control thanks to CEC (Consumer Electronics Control), a technology included in HDMI and common to many new multimedia devices. For instance, no special programming is needed to switch on the TV, DVD player and receiver with the TV remote at the same time, and to adjust the system volume using just one button.
Huge installed base
HDMI has emerged as the preferred digital connectivity standard since it was introduced 10 years ago.
According to market research company In-Stat, 5 million HDMI devices were sold in 2004, 63 million in 2006 and 228 million in 2008. In-Stat forecasts that 1 150 licensed HDMI adopters will ship over 800 million HDMI-compliant products in 2012, an increase of 17% over 2011. This will translate into a worldwide installed base of over 3 100 million HDMI products.
This huge market is the result of HDMI becoming the de facto digital AV interface standard and also because it offers a wide range of cables and connectors to meet different needs. The current HDMI 1.4 specifications propose five cable types to choose from, each designed to meet a particular performance standard.
HDMI 1.4 also defined two new connectors, a "Type D" micro connector, approximately 50 % smaller than its mini connector and roughly the size of a mini USB connector, and a "Type E" connector for automotive connection.
The micro connector is designed for mobile phones, pocket cameras and other portable devices. It features a full 19-pin array, like other HDMI connectors, and can handle 1080p video signals, bringing full HDTV resolutions to handheld devices.
HDMI connection is a must for any current AV device. However, its installation is not free: HDMI adopters pay an annual fee of USD10 000 (with special arrangements for low-volume producers); they also pay a royalty of between 4 and 15 US cents per unit sold, depending on use of the HDMI logo and of the HDCP (High-bandwidth Digital Content Protection) copy protection scheme that is backed by major content producers. Given the growing number of licensed HDMI adopters, the installed base and the sales forecast for HDMI-enabled devices, this interface is proving a very profitable development for its founders.
With its potential for further evolution to support technological innovations and the demands of the AV and multimedia industries, HDMI is looking at a bright future.