The High Definition Multimedia Interface first appeared in 2003 and was designed as a digital replacement for the multitude of analogue formats used in consumer AV standards (RF, SCART, Composite, S-VHS, RGB and so forth), in a compact single cable.
It can carry any uncompressed TV signal with 48-bit colour and up to eight channels of audio as well as control connections for the rare instances where one bit of kit can control another.
A DVI signal is fully compatible, so you can use a DVI to HDMI Cable converter no probs (although not for the analogue signals on DVI-A obviously).
The standard was put together by a consortium of big names, including Panasonic, Sony, Philips and Toshiba. The specification has now reached version 1.4.
The big gain in the later versions is the maximum clock speed, which governs bandwidth. The original specification called for a maximum of 165MHz, which is just enough to handle 1080p.
Version 1.3 upped this to 340MHz, in order to comfortably handle 1600p (technically known as Wide Quad Extended Graphics Array). The maximum data rate is 10.4GB/s.
It comes in single-link or double-link types (the 19-pin Type A and 29-pin Type B respectively), Type B equates to dual-link DVI, although we haven't seen one yet.
HDMI 1.4 launched in March 2010 and adds an Ethernet connection, an audio return channel, more control protocols and is ready for 3D signals. It can cope with a 4096 x 2160 display, enough for a very beefy home cinema setup.
Cables come in two main types: Standard or Category 1 cables can cope with the lower capacities of version 1.0 to 1.2, while High-Speed or Category 2 cables are certified for versions 1.3 to 1.4.
There's no standard set for the maximum cable length, its essentially down to the cable company to get it working properly. The signal drops off and the longer the cable, the thicker the wire and therefore the better the quality required.
Three years after HDMI first made its way into homes, DisplayPort was unleashed into the world. The standard was hammered out by VESA and was designed principally to go betwixt graphics card and monitor.
Importantly, it also happens to be royalty-free (as opposed to the four cent per device royalty charged to HDMI devices). DisplayPort was adopted after the United Display Interface (UDI) standard, principally developed by Intel as a DVI replacement, was canned.
Unlike the aforementioned HDMI, DisplayPort is a completely new standard. This means that it isn't possible to produce an easy connection converter in the same way it was for HDMI.
Having said that, there is a special DP++ port, which offers multi-mode connections (including single-link HDMI and DVI signals) and can be used with a suitable converter cable. It is all a bit of a fudge, though, and requires a non-standard physical port.
DisplayPort uses a packet-based transmission system, enabling flexible use of bandwidths. It comes in one-, two- and four-link versions with increasing data capacities.
Theoriginal version could transfer a maximum of 8.64GB/s, while the 1.2 specification (which has been around since December 2009) doubles this to a delectable 17.28GB/s – considerably more than HDMI.
DisplayPort specifies a maximum cable length of three metres for copper and fifteen meters or more for fibre optic. If you are serious about putting space between box and monitor, then this is clearly the display interface of choice.
DisplayPort was designed from the outset with direct graphics card/monitor connection in mind, including the internal one. It can run a monitor directly from the Displayport Cable signal, with no Low Voltage Differential Signalling (LVDS) circuitry required on the panel.