What is HDMI

HDMI

HDMI stands for High Definition Multimedia Interface. Its sole purpose is to transfer uncompressed digital video and audio signals through a compact cord. HDMI is capable of transferring any type of video format be it standard or digital and up to eight audio channels. HDMI is electrically similar to a DVI connection. Because the two are similar, HDMI and DVI are interchangeable and no signal loss will be experienced if a conversion between connections is necessary. These conversions can be achieved with a DVI to HDMI or HDMI to DVI connector. DVI is commonly found on personal computers and to connect your high definition capable video card to a compatible high definition television, an adapter is necessary. Typically HDMI cables are used for the transfer of HD content from Blu-Ray players and video game consoles such as the XBOX 360 and the Playstation 3 all of which utilize a high definition video signal.

Transfer Capabilities

An HDMI cable is capable of transferring data at up to 10.2 gigabits per second at a frequency of 340 MHz. It supports video resolutions of 480i/p, 576i/p, 720p, 1080i/p, 1440p, and 1600p. In terms of audio transfer it can transport audio signals following the standards of LPCM, Dolby Digial, DTS, DVD-Audio, Super Audio CD, Dolby TrueHD, and DTS-HD audio.

Cable Categories

The “standard”frequency at which HDMI operates now is 340MHz. This frequency is capable of transferring video with a resolution of up to 1600p. The lower quality version of HDMI cables operate at 74.5MHz and are only capable of resolutions up to 1080i. Because of the nature of signal degradation and attenuation, cables fall into two different categories. Category 1 cables are called standard cables and are rated at up to 74.5MHz. Category 1 cables usually average about 15 feet in length (5 meters). Anything longer than that and it is usually rated as a category 2. This is not to say that the Category 1 cables are incapable of transferring data at a higher frequency, it is just that the signal degradation in the quality of materials used in Category 1 cables cannot be guaranteed to be negligible whereas Category 2 cables can be.

CEC

All HDMI cables must be wired for CEC (Consumer Electronics Control). This means that the end user must be able to, if he wants, control all of his/her HDMI enabled devices with a single remote. The cables are wired all the same way so that integration between them using a single control unit is very easy.

Versions

There have been multiple version of the HDMI cable protocol over the years. These version are 1.0, 1.1, 1.2 and 1.2a, 1.3, 1.3a, 1.3b, 1.3b1, and 1.3c. All of the cables are produced with the same materials but each subsequent version of the cable is capable of transferring more features than its predecessor. Features such as auto-lip sync, Dolby TrueHD, and DTS-HD Master audio are available in the later versions of the cable but not in the previous ones. Purchasing an older HDMI cable does not guarantee that you will be able to take advantage of these features in your cable. To obtain some of these you will need to purchase one of the newer cables.