High Definition Multimedia Interface (HDMI)

HDMI is the first industry-supported, uncompressed, all-digital audio and video interface.

HDMI provides an interface between any audio/video source, such as a satellite or cable TV box, Blu-ray player and A/V receiver and an audio and/or video monitor, such as a plasma or projector.

HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It transmits all HDTV standards and supports up to 12-channel digital audio, ie Dolby 10.2.

The HDMI connector is sometimes referred to by its full name of 'HDMI type A'.

HDMI is retro compatible with the video only DVI-D because they both use they same video protocol; you just need a physical adaptor to convert between them.

The quality of HDMI video is identical to that produced by a DVI-D system, with the result that, as with the DVI system, any weaknesses in poor quality DVD hardware and software will be shown up.

For HDMI matrix switchers, click here.

HDMI evolution

Most of the current equipment and cables are 1.3b or 1.4.

HDMI 1.2

HDMI 1.2 devices and equipment support One Bit Audio format, such as SuperAudio CD's DSD (Direct Stream Digital). This specification offers better support for current PCs with HDMI outputs, including the use of HDMI Type A connectors for PC sources and displays with full support for PC video formats.

HDMI1.3b

After HDMIv1.2 came HDMIv1.3b which enables the current generation of HDTVs, PCs and Blu-ray players to transmit and display content in billions of colours with unprecedented vividness and accuracy.

The HDMI 1.3b specification more than doubled HDMI’s bandwidth and added support for Deep Colour technology, a broader colour space, new digital audio formats (Dolby TrueHD and DTS-HD Master Audio) and automatic audio/video synching capability (“lip sync”).

HDMI 1.4a (usually shortened to HDMI 1.4)

The HDMI v1.4 specification (introduced in March 2010) includes:

• An Ethernet channel on HDMI cables to consolidate HD video, audio, and data in a single cable, to enable high speed bi-directional communication to enable IP-based applications over HDMI such as DLNA, UPnP, and IPTV, and to permit transfer speeds up to 100Mbps, ie required for IPTV
• A digital audio return to simplify cabling by combining the upstream audio capability into a single HDMI cable, ideal for TVs with built-in tuners that receive surround sound, eg Freesat TVs and FreeviewHD TVs
• Definition of common 3D formats and resolutions, 3D support for up to 1080p resolution and support for many 3D techniques, ie required for 3DTV, see below.
• Support for 4K x 2K resolution (the next resolution after 1080p)
• Enables simple, automated picture setting selection with no user intervention

Most cables will not be marked as HDMIv1.4 (or 1.4a). They should be marked 'standard speed with ethernet' or 'high speed with ethernet' by these logos.

Which cables should I use for 3D?

'HDMI v1.4' cables must handle 3D broadcast video up to a resolution of 720p/60Hz or 1080i/60Hz (This is not Sky 3D which is at a lower resolution). This means they must be capable of transfer speeds of 1.98Gbps (720p/60) and 2.23 Gbps (1080i/60Hz).

They must also be able to handle 3D Blu-ray movie at 1080p/24fps, ie a band width of 3.56Gbps.

All standard speed with ethernet cables meet these requirements.

High speed with ethernet cables have a bandwidth of 10.2Gbps and are capable of handling 1080p/60Hz resolution (which requires 8.92Gbps). No 3D equipment is yet offering 1080p/60.

For a summary of the HDMI version features click here >>> .