What is HDMI ?
HDMI stands for High-Definition Multimedia Interface. It is the first and only industry-supported, uncompressed, all-digital audio/video interface.
By delivering crystal-clear, all-digital audio and video via a single cable, HDMI dramatically simplifies cabling and helps provide consumers with the highest-quality home theater experience.
HDMI provides an interface between any audio/video source, such as a set-top box, DVD player, or A/V receiver and an audio and/or video monitor, such as a digital television (DTV), over a single cable.
HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable.
It transmits all ATSC HDTV standards and supports 8-channel, 192kHz, uncompressed digital audio and all currently-available compressed formats (such as Dolby Digital and DTS), HDMI 1.3 adds additional support for new lossless digital audio formats Dolby TrueHD and DTS-HD Master Audio with bandwidth to spare to accommodate future enhancements and requirements.
HDMI is the de facto standard digital interface for HD and the consumer electronics market:
More than 700 companies have become adopters, and nearly 200 million devices featuring HDMI are expected to ship in 2008, with an installed based of nearly one billion HDMI devices by 2010 (conservative estimates by In-Stat).
HDMI is the interface for convergence of PC and consumer electronics devices: HDMI enables PCs to deliver premium media content including high definition movies and multi-channel audio formats.
HDMI is the only interface enabling connections to both HDTVs and digital PC monitors implementing the DVI and HDMI standards.
HDMI is continually evolving to meet the needs of the market: Products implementing new versions of the HDMI specification will continue to be fully backward compatible with earlier HDMI products.
The Market Adopts HDMI
HDMI has become so successful, so quickly, because it meets the needs of all facets of the Consumer Electronics and PC ecosystem. Manufacturers now have an all digital pipeline from the source material to the display;
content providers have an interface that protects their intellectual property; and consumers have and easy-to-use, high quality, plug-and-play interface for their home entertainment environment.
Quality: HDMI maintains the audio in its pure digital form all the way to the amplifier. Analog audio connections are more prone to losses depending on the cabling and other electronics of the audio rendering device.
Compared to SPDIF connections, HDMI has significantly more bandwidth, allowing it to support the latest lossless audio formats such as Dolby TrueHD and DTS-HS Master Audio.
These formats can not be supported over SPDIF connections due to their very high data rate requirements that exceed the capabilities of SPDIF. Please also see section on HDMI 1.3 for further details on Dolby TrueHD and DTS-HD Master Audio formats.
Ease of Use: HDMI combines video and multi-channel audio into a single cable, eliminating the cost, complexity, and confusion of multiple cables currently used in A/V systems.
This is particularly beneficial when equipment is being upgraded or added.
Intelligence: HDMI supports two-way communication between the audio source (such as a DVD player) and the audio rendering device (such as an A/V receiver), enabling new functionality such as automatic configuration and one-touch play.
By using HDMI, devices automatically deliver the most effective format (e.g. Dolby Digital vs. 2-channel PCM) for the A/V receiver that it is connected to – eliminating the need for the consumer to scroll through all the audio format options to guess what is best and properly supported.
With the advent of high-definition content, analog interfaces were becoming increasingly limited in their ability to deliver the highest quality, high-definition content.
HDMI has no conversion or compression of signals:
With the delivery of 1080p content, analog interfaces are nearing the end of their ability to deliver high-definition content without highly compressing the signal, which can result in loss of data and signal quality.
HDMI has the bandwidth to send uncompressed video so there is no loss of data or signal quality
Content Protection allows access to HD content:
Content providers, including all the major movie studios, have been clear that much of the studio content will not be released in high-definition over unprotected analog interfaces.
They have designated HDMI and/or DVI as the only interfaces that will be allowed to carry this new HD content.
HDMI Digital allows two-way communication:
HDMI supports two-way communication between the video source (such as a DVD player) and the DTV, enabling new functionality such as automatic configuration and one-touch play. By using HDMI, devices automatically deliver the most effective format (e.g. 480p vs. 720p, 16:9 vs. 4:3) for the display that it is connected to – eliminating the need for the consumer to scroll through all the format options to guess what looks best.
HDMI & Entertainment Systems
The most tangible and immediate way that HDMI changes the way we interface with our components is in the set-up. One cable replaces up to 11 analog cables, highly simplifying the setting up of a home theater as well as supporting the aesthetics of new component design with cable simplification.
Next, when the consumer turns on the HDMI-connected system, the video is of higher quality since the signal has been neither compressed nor converted from digital to analog and back.
Lastly, because of the two-way communication capabilities of HDMI, components that are connected via HDMI constantly talk to each other in the background, exchanging key profile information so that content is sent in the best format without the user having to scroll through set-up menus.
The HDMI specification also includes the option for manufacturers to include CEC functionality (Consumer Electronics Control), a set of commands that utilizes HDMI’s two-way communication to allow for single remote control of any CEC-enabled devices connected with HDMI.
For example, CEC includes one-touch play, so that one touch of play on the DVD will trigger the necessary commands over HDMI for the entire system to power on and auto-configure itself to respond to the command.
CEC has a variety of common commands as part of its command set, and manufacturers who implement CEC must do so in a way that ensures that these common command sets interoperate amongst all devices, regardless of manufacturer.
CEC is an optional feature, however, so consumer interested in this functionality must look for CEC in the product feature list. Also, it is important to know that some manufacturers are creating their own proprietary names for their implementation of the CEC command set.
How many inputs/outputs do you need?
More and more inputs and outputs on components are appearing as more and more people are connecting with HDMI. It is common to see 3 and 4 inputs on an HDTV – many with one input on the side or front for connecting to game consoles or other portable devices such as digital still cameras or camcorders.
Always think about the number of sources and displays (or projectors) that could become part of your home theater system, and make sure the device you are evaluating has the number of inputs and outputs to support your needs over the near and long term.
For those who have existing systems with one or two inputs, and are finding they need more, there are HDMI switches in the market that switch from multiple inputs (sources) to one output (to your display).
Think features rather than HDMI version number.
HDMI is constantly evolving to meet the needs of the marketplace. The standard is constantly adding more and more features that manufacturers can implement if they desire. But HDMI does not require manufacturers to implement everything that HDMI can do.
HDMI provides a menu of capabilities and allows the manufacturer to choose which of those features make sense for its product line.
As a result, it is recommended that consumers look for products with the features they want, rather than the version number of the HDMI components.
Version numbers reflect capabilities, but do not correspond to product features. For example, if you want the new video features called Deep Color, look for Deep Color in the feature set rather than HDMI 1.3, the version of the specification that enabled Deep Color.
Why? Because the version of the specification that enables Deep Color (1.3) does not mandate that Deep Color functionality be implemented.
However, it is important to also note that all HDMI versions are backwards compatible, so not matter what version of HDMI is in the component, all HDMI-enabled components will work together at the highest level of shared functionality.
Convergence Between The PC And Consumer Electronics
HDMI was developed using the same technology as DVI (Digital Visual Interface), the digital connection standard for the PC environment. So, HDMI is fully compatible with all DVI-enabled PCs (since HDMI offers both audio and video over one cable, and DVI carried only video, DVI-HDMI connectivity requires a separate audio cable).
HDMI enables PCs to deliver premium media content including high definition movies and multi-channel audio formats. HDMI is the only interface enabling connections to both HDTVs and digital PC monitors implementing the DVI and HDMI standards – fully compatible with the hundreds of millions of DVI displays already in the market.
Recently, the HDMI standards body announced that cables would be tested as Standard or High-Speed cables.
- Standard (or “category 1”) cables have been tested to perform at speeds of 75Mhz, which is the equivalent of a 1080i signal.
- High Speed (or “category 2”) cables have been tested to perform at speeds of 340Mhz, which is the highest bandwidth currently available over an HDMI cable and can successfully handle 1080p signals including those at increased color depths and/or increased refresh rates. High-Speed cables are also able to accommodate higher resolution displays, such as WQXGA cinema monitors (resolution of 2560 x 1600).
Does HDMI accommodate long cable lengths?
HDMI technology has been designed to use standard copper cable construction at long lengths. In order to allow cable manufacturers to improve their products through the use of new technologies, HDMI specifies the required performance of a cable but does not specify a maximum cable length. We have seen cables pass “Standard Cable” HDMI compliance testing at lengths of up to a maximum of 10 meters without the use of a repeater.
It is not only the cable that factors into how long a cable can successfully carry an HDMI signal, the receiver chip inside the TV or projector also plays a major factor. Receiver chips that include a feature called “cable equalization” are able to compensate for weaker signals thereby extending the potential length of any cable that is used with that device.
With any long run of an HDMI cable, quality manufactured cables can play a significant role in successfully running HDMI over such longer distances.
Q. How can I tell the differences in each version of the HDMI specification?
Download a copy of the most recent specification of HDMI. At the beginning of the document, there is a section called “Revision History.” In this section, you can view all of the the changes for each revision of the Specification.
Q. Are all of the new HDMI versions backward compatible with previous versions?
Yes, all HDMI versions are fully backward compatible with all previous versions.
Q. What’s new in the HDMI 1.3 Specification?
- Higher speed: Although all previous versions of HDMI have had more than enough bandwidth to support all current HDTV formats, including full, uncompressed 1080p signals, HDMI 1.3 increases its single-link bandwidth to 340 MHz (10.2 Gbps) to support the demands of future HD display devices, such as higher resolutions, Deep Color and high frame rates. In addition, built into the HDMI 1.3 specification is the technical foundation that will let future versions of HDMI reach significantly higher speeds.
- Deep Color: HDMI 1.3 supports 10-bit, 12-bit and 16-bit (RGB or YCbCr) color depths, up from the 8-bit depths in previous versions of the HDMI specification, for stunning rendering of over one billion colors in unprecedented detail.
- Broader color space: HDMI 1.3 adds support for “x.v.Color™” (which is the consumer name describing the IEC 61966-2-4 xvYCC color standard), which removes current color space limitations and enables the display of any color viewable by the human eye.
- New mini connector: With small portable devices such as HD camcorders and still cameras demanding seamless connectivity to HDTVs, HDMI 1.3 offers a new, smaller form factor connector option.
- Lip Sync: Because consumer electronics devices are using increasingly complex digital signal processing to enhance the clarity and detail of the content, synchronization of video and audio in user devices has become a greater challenge and could potentially require complex end-user adjustments. HDMI 1.3 incorporates automatic audio synching capabilities that allows devices to perform this synchronization automatically with total accuracy.
- New HD lossless audio formats: In addition to HDMI’s current ability to support high-bandwidth uncompressed digital audio and all currently-available compressed formats (such as Dolby® Digital and DTS®), HDMI 1.3 adds additional support for new lossless compressed digital audio formats Dolby TrueHD and DTS-HD Master Audio™.
Q. What is the difference between DVI and HDMI?
HDMI is DVI with the addition of:
- Audio (up to 8-channels uncompressed)
- Smaller Connector
- Support for YUV Color Space
- CEC (Consumer Electronics Control)
- CEA-861B InfoFrames
Yes, HDMI is fully backward compatible with DVI compliant devices.
HDMI DTVs will display video received from existing DVI-equipped products, and DVI-equipped TVs will display video from HDMI sources.
However, some older PCs with DVI are designed only to support computer monitors, not televisions.
Consumers buying a PC with DVI should make sure that it specifically includes support for television formats and not just computer monitors.
Also, consumers may want to confirm that the DVI interface supports High-bandwidth Digital Content Protection (HDCP), as content that requires HDCP copy protection will require that both the HDMI and DVI devices support HDCP to properly view the video content.