Thursday, August 20, 2015

What is HDMI

What is HDMI


What is H D M I (High Definition Media Interface)?

In simple terms, HDMI is an all digital connection that can carry high-definition video and several digital audio channels all over the same cable. HDMI was first officially unveiled in 2003 but it is only in the last few years that we have seen widespread support for the standard. During the development of HDMI several versions from 1.1 until now 1.4 have been developed. The different versions signify changes to the types of audio they can transmit, all versions should be able to transmit HD video up to 1080p.
1.0 was the first version of HDMI and was ratified in late 2002, it will decode most versions of audio content in DVD and digital TV signals including Dolby Digital and DTS. All HDMI Category 1 Cables are certified up to 720p/1080i.

1.1 this version added DVD – Audio support which means, users with compatible discs and players can listen to 5 channel audio streams without the need for six separate audio RCA cables.

1.2/1.2a: the main improvement of this version over the previous one is the addition of super audio CD support which means users no longer need to rely on I link or analogue cables to listen to super audio. The standard also adds support for an, as yet, unused type of PC connection.

1.3/1.3 a/1.3b/1.3c: these versions added support for Dolby and to high-definition and DTS – HD Master audio, which are used in Blue-ray players. Increasingly, audio and visual receivers are including decoding for these standards on board, while devices like the PlayStation 3 will output the coded signals. The 1.3 standard also increases the available bandwidth by a factor of 2 to 10 Gbps. Although versions 1.3b and 1.3c exist they don't add any further functionality over 1.3 a and so are interchangeable.

1.4 this is the product's biggest update since HDMI was released and introduces a host of new features and a modified cable design. The biggest new feature is the introduction of ethernet to HDMI, which allows a two-way hundred megabit connection to pass between two compatible components and means you will no longer need to wire your system up this land cables as well however, ethernet is an optional feature and not all versions of 1.4 cables supported. You should look for cables marked easy or ”with ethernet.

The 1.4 standard also supports 3-D in full 1080p resolution, where version 1.3 only supports 1080i resolution up to (3840/2160p).
HDMI v1.4 cables support up to 3840×2160 24Hz/25Hz/30Hz, 4096×2160 24Hz.
DSTV / Multichoice currently broadcast their HD Channel on HD 720 (1280 x 720) - 720p.

The new version allows for an audio return channel which is especially handy for television viewers. If you are watching your televisions 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 for better compatibility with digital still cameras.

The two standards are inter-compatible with each other, but to use HDMI ethernet you will need to own dedicated versions of 1.4 cable products, which support the new version. They have been available from early 2010.

But how does HDMI differ to analogue cables?
Analogue video cables, such as component, composite or s – video, are currently still the main methods used to transfer picture signals in an average home system. Component is a highest quality analogue cable, since it breaks down the picture signals into three different cables - one cable each for red, blue and green. When you have got analogue cabling connecting digital sources (such as an LC D or plasma screen with a DVD), the digital video or sound signals have to be converted into analogue to travel through the cable, before being reconverted back into digital at the receiving end. This could lead to some signal degradation and the 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 the video or audio signal. HDMI pictures should be smoother and sharper with a distinct reduction in video noise. Sound should be crisp and taught, without any distortion. And of course using the single cable HDMI is a lot less messy, than all the additional 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. And HDMI cable allows you to exactly match pixel by pixel in the native resolution with whatever source device you have 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.

What is the difference between DVI and 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 then HDMI. DVI was initially developed as a connection between PCs and monitors, but eventually found its way into the home entertainment world as well.
The HDMI standard is actually based on the DVI standard, therefore the picture quality should be the same. One advantage of HDMI is the capability of transmitting audio signals, which DVI cannot do, HDMI cables can also be longer than DVI cables, HDMI cables can be up to 20 m in length.
For more information about D V I and conversion from HDMI to DVI see our article on DVI.
(With thanks to CNET Australia).