The Ins and Outs of HDMI The essential connection for high-definition home theater

Steve Kindig — Aug 31, 2009

Article contents
Page 1.   HDMI: High-def video and ultra-detailed sound
Page 2.   HDMI versions, evolving at digital speed
Page 3.   Hooking up with HDMI: issues and answers

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An evolving standard

In this fast-changing era of new formats and technologies, HDMI is the accepted universal connector for digital home entertainment. The HDMI spec was developed by a group of companies including Hitachi, Matsushita (Panasonic), Philips, Silicon Image, Sony, Thomson (RCA), and Toshiba. It's also supported by movie studios like Fox, Universal, Warner Bros., and Disney, as well as satellite providers DIRECTV® and DISH™ Network, and CableLabs® (an R&D consortium that develops new technologies for cable TV operators). Over 800 companies currently build HDMI-equipped products.

Many new TVs have two or more HDMI inputs. The lower input includes stereo audio jacks for backward compatibility with DVI-equipped video components.

The HDMI standard continues to evolve to meet the needs of high-performance home theater equipment. All versions of HDMI are backward compatible with previous versions, as well as with DVI (however, a DVI connection passes video only, not audio). Part of the built-in intelligence of HDMI enables it to automatically send the highest quality video and audio formats that are mutually supported. In other words, if you connect two devices, one with HDMI version 1.1 and the other with 1.2, the system will be limited to the 1.1 feature set.

Although you'll often see the HDMI version listed as part of a component's specifications, it's probably best not to pay much attention to it. For specific details about a particular component's audio and video capabilities, you're better off focusing on the component's feature list. A product's HDMI version by itself doesn't mean that all the latest features have been implemented; it does not guarantee a particular feature set. The reason is that the capabilities listed for each version of HDMI are optional, not mandatory.

It's up to each manufacturer to decide which HDMI features to build into its gear. A perfect example is 1080p video input capability. Although the original HDMI 1.0 spec included 1080p video (before 1080p TVs even existed!), it wasn't until 2006 that a significant number of HDTVs included 1080p-capable HDMI inputs.

Do I need to worry about compatibility between HDMI versions?
Although there have been multiple versions of the HDMI spec, there haven't been any physical changes to the HDMI connectors on cables and components. That means you don't have to worry about buying a cable that's "rated" for a particular HDMI version. Plus, each new HDMI version is backwards compatible with older versions, so your older and newer HDMI-equipped components can generally still work together.

So what are the differences between different HDMI versions? Take a look at our summary of HDMI's evolution below:

HDMI 1.0: The original spec called for a single-cable digital audio/video connection with 165MHz bandwidth and a maximum bitrate of 4.9Gbps (enough for 1080p video). Two-channel audio only. Released December, 2002.
HDMI 1.1: Added multichannnel audio support for DVD-Audio (up to 5.1 channels). Released May, 2004.
HDMI 1.2: Added support for multichannel one-bit audio formats like SACD (Super Audio CD). Included support for HDMI connectors on personal computers. Required displays with HDMI 1.2 or later to support future low-voltage devices. Released August, 2005.
HDMI 1.2a: Fully specified the Consumer Electronic Control (CEC) features and command sets for remote control functions. Required cable manufacturers to submit longer cable lengths for additional testing for spec compliance. For a device to pass 1.2a testing, all of its HDMI connectors required inspection and approval by HDMI Licensing, LLC. Released December, 2005.
HDMI 1.3: Increased bandwidth to 340MHz and the maximum bitrate to 10.2 Gbps (plus the capability for higher bandwidth in the future). Adopted the "Deep Color" standard, which supports 10-bit, 12-bit, and 16-bit color for over one billion possible colors — previous versions were limited to 8-bit. (Note: Because color information is based on three primary colors — red, green and blue — you'll sometimes see 1.3's enhanced color depth described as 30-bit, 36-bit, and 48-bit.) Added support for the "xvYCC" extended-gamut color space standard (also known as x.v.Color), which supports 1.8 times as many colors as existing HDTV signals. (No commercially available video content currently uses Deep Color or x.v.Color.) Added ability to output new lossless compressed digital audio formats (Dolby® TrueHD and DTS-HD Master Audio™) for decoding by a compatible A/V receiver. Incorporated automatic "lip sync" control for perfect audio/video timing (sometimes an issue when audio is sent to a surround receiver or processor and video is delivered directly to the display). Also made available a new mini-connector for use with smaller devices such as digital cameras and camcorders. Released June, 2006.
The 1.3 spec has been recently updated to 1.3a, followed by 1.3b. However, for consumers, there is no difference between versions 1.3, 1.3a or 1.3b. These are minor revisions that relate to manufacturing and testing issues and do not affect features or functionality.