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 signal, with no Low Voltage Differential Signalling (LVDS) circuitry required on the panel.
DISPLAYPORT: The full-size 20-pin DisplayPort plug, destined to be the connection of choice for monitors at a distance
DisplayPort is royalty-free. HDMI costs currently only four cents a pop, mind. DisplayPort has fewer rules over implementation too and is not so highly regulated, so manufacturers can have more fun with it.
Technically more accomplished, flexible and capable of carrying much more than just video and audio. At top-spec it has much more bandwidth too (10.2GB/s vs 17.28GB/s).
Supports multiple monitors on one cable, so you can daisy-chain two or more together. Thus, full DisplayPort 1.2 can drive four 1920 x 1200 monitors, one on each link, yowza.
Offers three metre copper cable at full resolution, its also been designed for fibre optics too, enabling much longer cables. HDMI has no maximum cable length and the signal can degrade.
It can run Direct Drive Monitors. This is of most significance internally in laptops, but we should see external DD monitors, which can be thinner, and one would hope, cheaper.
There's a bi-directional auxiliary channel, which can be used for input from a microphone or USB device. This can carry 1Mb/s on the first versions and 720Mb/s for version 1.2.
A proper cable retention system, a small point perhaps, but a possibly very annoying if your HDMI cable keeps falling out.
The other option: Wireless Display
Wired kit is passé. Where's our wireless connection? Well, Intel has WiDi, Wireless Display, which sends an HD signal across the room. You need a wireless router box wired-up to your telly's HDMI port.
Itimpressed the crowd at the Consumer Electronic Show in 2010, but don't you get too excited – these were suits.
It's perfect for getting PowerPoint from your laptop to a wall-mounted screen, but it's not fast enough for exciting stuff, such as games. It's laggy and testing has revealed that a lot of games freeze.
Plus, it only runs on certain Intel processors: 'M' models with integrated graphics – laptops basically. WiDi is aimed squarely at business apps, nothing to get excited about, then.
WHDI, Wireless Home Digital Interface, is more exciting. This is designed as a full AV wireless standard. The basic spec is for 3Gbps, enabling 1080p, and a range of a 100 feet. The aim is to broadcast Blu-ray from a player to screens around the house.
The players behind the standard include Sony, LG, Sharp, Hitachi and Motorola. It's all based around a special transmission system invented by Amimon, which assigns importance to individual bits, enabling error correction to be applied selectively.
WHDI: Plugs into your HDMI port and punts the signal off to a telly or receiver plugged into another HDMI port. We likey
In your video data, its the first value for a pixel element that's most important. Get this wrong and you'll get a completely whack colour, however get the last bit of a colour value wrong and you only get a very slight change in colour.
Thus the system squeezes Full HD video out of the 5GHz wireless signals licensed for domestic use by not being too fussy about dropped bits where you won't notice the difference.
All well and good for home entertainment systems, but the relatively low bandwidth means it'll be a nice extra for a PC rig, being able to send a movie or game to another screen, but it won't replace the primary display.
WHDI is due to be updated to cope with 3D and version 2.0 should bring higher bandwidths in the future. However, given the legal limits on the frequency and power levels of an unlicensed domestic wireless system, wireless will always struggle to offer the high resolutions of wired systems.
First published in PCFormat issue 248
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