HDTV stands for High Definition Television, and if you live in the USA, Australia, or Japan you may already have experienced it. There are three key differences between HDTV and what's become known as standard definition TV ie regular NTSC, PAL or SECAM. The three differences are; an increase in picture resolution, 16:9 widescreen as standard, and the ability to support multi-channel audio such as Dolby Digital.

The most important aspect of HDTV, and the one which gives it its name is the increased resolution. Standard definition NTSC broadcasts have 525 horizontal lines, and PAL broadcasts are slightly better at 625 lines. In both these systems however, the actual number of lines used to display the picture, known as the active lines, is fewer than that. In addition, both PAL and NTSC systems are interlaced, that is, each frame is spit into two fields, one field is the odd-numbered lines and the other is the even lines. Each frame is displayed alternately and our brain puts them together to create a complete image of each frame. This has an adverse affect on picture quality.

HDTV is broadcast in one of two formats; 720p and 1080i. The numbers refer to the number of lines of vertical resolution and the letters refer to whether the signal is progressive scan, 'p', or interlaced, 'i'. Progressive scan means that each frame is shown in its entirety, rather than being split into fields. Both systems are significantly better quality than either PAL or NTSC broadcasts.

HDTV uses 16:9 widescreen as is its aspect ratio so widescreen pictures are transmitted properly and not letterboxed or panned and scanned. Dolby Digital multichannel sound can be broadcast as part of an HDTV signal, so if you have a surround sound speaker set-up you can use it to listen to TV rather than just DVDs.

To receive an HDTV broadcast you need either a TV with a built-in HDTV tuner or a HDTV receiver which can pick-up off the air HDTV channels, or cable or satellite HDTV like. You also need to live in are where HDTV channels are broadcast or distributed by cable or satellite.

Currently HDTV is widespread in Japan and is becoming commonplace in the US, with most major networks distributing HDTV versions of their popular content. The 2005 Superbowl led to a large increase in the demand for Fox Sports HDTV and cable companies scrambled to add it to their offering in the run up to the game. In Autralia, HDTV uptake was sluggish initially but has increased significantly since 2003.

The situation in Europe is not so bright. There is only one company broadcasting HDTV in the whole of Europe, Euro1080, and it has only two HDTV channels, both in the 1080i format. Euro1080HDe shows major cultural and sporting events to cinemas and clubs around Europe, while HD1 broadcasts sports, opera, rock music, and lifestyle programs via satellite to homes in Europe. UK satellite broadcaster, Sky, which is owned by Fox proprieter Rupert Murdoch, has announced plans to broadcast some HDTV content in 2006. The BBC has also made noises about broadcasting HDTV programs (it already films some programs in HD format).

However, it will be a while before HDTV in Europe catches up with the rest of the world. The controversy created by the confirmation of plans by the UK government to start switching off analogue transmitters in 2008 showed how many people have yet to make the switch to DVB-T. That will be used as an argument to show that there is no appetite in the UK for another major change in TV broadcasting - particularly as most people think they already have 'digital TV' in the form of DVB-T.

Given that television was invented by a Briton, and Europe led the way with PAL for so long, this is a rather sorry state of affairs.

Kenny Hemphill is the editor and publisher of The HDTV Tuner - a guide to the kit, the technology and the programming on HDTV.