Blu-ray is an optical disc format which is set to rival HD-DVDin the race to be the de-facto standard storage medium for HDTV. The HD-DVD vs Blu-ray battle resembles that between Betamax and VHS and DVD+RW and DVD-RW.

Currently, the major Hollywood film studios are split evenly in their support for Blu- ray and HD-DVD, but most of the electronics industry is currently in the blue corner.

The key difference between these new players and recorders and current optical disc technology is that Blu-ray, as its name suggests, uses a blue-violet laser to read and write data rather than a red one. Blue light has a shorter wavelength than red light, and according to the Blu-ray Disc Association (BDA), which is made up of, amongst others, Sony, Philips, Panasonic, and Pioneer, this means that the laser spot can be focussed with greater precision.

Blu-ray discs have a maximum capacity of 25GB and dual-layer discs can hold up to 50GB - enough for four hours of HDTV. Like HD-DVD, Blue laser discs don't require a caddy and the players and recorders will be able to play current DVD discs. Codecs supported by Blu-ray include the H.264 MPEG-4 codec which will form part of Apple's QuickTime 7, and the Windows Media 9 based VC-1.

The BDA says that although blue laser discs and players are already shipping in Japan, they won't ship in the US until the end of 2005 at the very earliest. It is likely that players will be very expensive initially, compared to DVD players. In Japan, they cost the equivalent of $2000. However, as with all new technology, prices will quickly fall - particularly as Blu-ray will be competing with HD-DVD for that space under your TV.

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