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High Definition Multimedia Interface, or HDMI, is hailed as the next generation of audiovisual cabling. Simply put, HDMI is an all-digital connector that can carry high-definition video and several digital audio channels all on the one cable. HDMI was first officially unveiled in 2003, but it's only in the last few years that we've seen widespread support for the standard. Is it something you should be seeking out?
An HDMI connector from Monster Cable (Credit: Monster Cable)
How is it different from my current analog cables?
Analog video cables, such as component, composite or S-Video, are currently the main methods used to transfer picture signals in an average home system. Component is the highest quality analog cable as it breaks down the picture signal into three different cables — one each for red, blue and green. When you've got analog cabling connecting digital sources (such as an LCD or plasma screen with a DVD), the digital video or sound signals have to be converted into analog to travel through the cable, before being re-converted back into digital at the receiving end. This could lead to some signal degradation and a resulting loss in output quality.
What are the advantages of going digital with HDMI?
HDMI can deliver high quality sound or vision without the risk of quality loss due to the conversion or compression of a video or audio signal. HDMI pictures should be smoother and sharper, with a distinct reduction in video noise. Sound should be crisp and taut, without any distortion. And, of course, using the single cable HDMI can get rid of a lot of messy cables snaking around your home theatre kit.
Because of its digital nature, HDMI also works well with fixed-pixel displays such as LCD, plasma or DLP screens and projectors. An HDMI cable allows you to exactly match pixel by pixel in the native resolution of the screen with whatever source device you've got connected. HDMI systems will also automatically convert a picture into its most appropriate format, such as 16:9 or 4:3.
HDMI has some built-in smarts that allow you to control any device connected via HDMI through the one remote. Since the HDMI connection allows two-way communication between devices, it gives you basic universal remote-like functions which, for example, can tell the components in an HDMI-linked system to turn on when you want to watch a DVD, just with the press of a button.
How does DVI fit into the equation? Is it better than HDMI?
You may have heard of digital video interface (DVI), which is another all-digital connector for video. DVI has been around for longer, and can be found in many more televisions and other devices than HDMI. DVI was initially developed as a connector between PCs and monitors, but eventually found its way into the home entertainment world.
HDMI connectors (right) are smaller than DVI plugs
(Credit: Monster Cable)
The HDMI standard is actually based on DVI, so picture quality should be identical. Where HDMI has it over DVI is its audio capabilities — DVI can only carry video signals. HDMI cables can also be made longer than DVI — HDMI can go up to 15m in length. And from an aesthetic viewpoint, HDMI connectors are less bulky than DVI ones. HDMI connects like a USB device for PCs, while DVI still has screw pins on its connector. However, this means that HDMI connections are more prone to damage from accidental knocks so more care needs to be taken with them.
I've got some gear with DVI connectors. Will they work with HDMI?
HDMI is fully backwards compatible with DVI, so you won't be making your DVI products obsolete if you buy something with an HDMI connector. For example, HDMI televisions will display video received from existing DVI-equipped products, while an HDMI DVD player will play on a DVI-equipped television. All you'll need is an HDMI/DVI adapter. Just be aware that doing this will lose you the added functionality of HDMI, such as automatic screen format conversion and universal remote control.
What products support HDMI?
HDMI has been on the market for a while now, and most new DVD players, set-top boxes and TVs feature at least one HDMI port.
On the display side of the equation, most new screens, projectors and DVD players support the standard. If you're looking to buy a device like a TV or AV receiver look for the most HDMI ports you can afford. Three is the minimum you should expect from today's devices, while DVD players and the like only usually require one output. Also, be aware that an HDMI port currently only sends information in one direction — though there are moves to change this in the future. As a result, it's not possible to use an HDMI output port on a PC, for example, to display a PS3 signal.
Where can I get HDMI cables?
If you own a component with HDMI but don't have a cable for it, then there are several cable manufacturers which sell HDMI gear. There has been a lot of debate about HDMI cables and how much you should pay for them. We can say that we've had good experiences with the AU$20 cables from EzyHD as well as the more esoteric and expensive cables. Belkin, for example, sells HDMI cables and HDMI to DVI cables under its Pure AV range of interconnects. Monster Cable also has a comprehensive selection of HDMI products. HDMI cables and adapters by Monster Cable have been developed in a joint partnership with HDMI's founder, Silicon Image. Electrically they all appear to be similar, and in the end what you're paying for is reliability and build quality. But as we say, don't save money on a TV just to then blow it on a cable.
A Pioneer screen with HDMI connectors (Credit: Pioneer)
What do the different versions mean?
While the latest version of HDMI is up to 1.4, there are four main versions that most equipment will correspond to — 1.0, 1.1, 1.2 and 1.3. Notice that the versions signify changes to the types of audio they can transmit, as all versions should be able to transmit HD video up to 1080p.
1.0: this is the first version of HDMI and it was ratified in late 2002. It will decode most versions of audio contained in DVD and digital TV signals, including Dolby Digital and DTS.
1.1: this version added DVD-Audio support, which means users with compatible discs and players can listen to 5.1 channel audio streams without the need for six separate audio RCA cables.
1.2/1.2a: The main improvement on 1.1 is the addition of Super Audio CD (SACD) support, which means users no longer need to rely on iLink or analog cables to listen to SACDs. The standard also adds support for an as-yet unused Type A PC connector.
1.3/1.3a/1.3b/1.3c: version 1.3 adds support for Dolby TrueHD and DTS-HD Master Audio which are used in Blu-ray players. Increasingly, AV receivers are including decoding for these standards on board, while devices like the PlayStation 3 will output decoded signals. The 1.3 standard also increases the available bandwidth by a factor of two to 10Gbps. Though 1.3b and 1.3c exist they don't add any further functionality over 1.3a, and so are interchangeable.
What's new in version 1.4?
Version 1.4 is the product's biggest update since HDMI was released, and introduces a host of new features and a modified cable design.
The big new feature is HDMI Ethernet which allows a two-way 100Mb connection to pass between two compatible components and means you will no longer need to wire your system up with LAN cables as well. However, Ethernet is an optional feature and not all version 1.4 cables support it — look for cables marked "-E" or "with Ethernet".
The 1.4 standard also supports 3D in full 1080p resolution — version 1.3 only supports 1080i — and resolutions up to 4K/2K (3840/2160p).
The new version allows for an audio return channel which is especially handy for television viewers. If you're watching your television's on-board tuner it means you can now hear it through your sound system with just the single cable — no need for a separate optical cable.
Two new connector systems will also debut with 1.4, a new 19-pin HDMI Micro Connector (Type D) which is half the size of the current Mini, and the Automotive Connection System (Type E) which is designed to withstand the rigours of in-car use.
Lastly, HDMI will now support photographic colour standards including sYCC601, Adobe RGB and Adobe YCC601 for better compatibility with digital still cameras.
The two standards are inter-compatible with each other, but to use HDMI Ethernet you'll need to own dedicated version 1.4 cables. Products which support the new version will be available from early 2010.