Historic fight

Many people liken the fight to the 1980s tussle between VHS and Betamax. Then, Sony lost out to rival JVC in the format wars.

This time, the electronics giant will be hoping that it will come out on top.

Backers of its technology include Samsung, Dell and Apple, while Toshiba, with NEC, Microsoft and others, is pushing HD DVD.

In Hollywood, companies like Disney and 20th Century Fox have sided with Sony, while the followers of HD DVD include Universal.

Warner Bros and Viacom have said they will support both.

Film extras

Both systems are incompatible but can both store large amounts of data, important for high-definition video.

The technologies use a blue laser to write information. It has a shorter wavelength so more data can be stored.

The first Blu-ray discs can store 25GB of high-quality data, but will eventually be able to store 50GB.

Toshiba's HD DVD will hold 30GB.

By comparison, a standard single-layer DVD holds just under 5GB of data

Both disc formats offer much better quality audio and video, and the ability for film-makers to pack many more extras onto a single disc.

They will also be more user-friendly, allowing users to switch languages or skip scenes without having to return to the main menu.

Games technology

The first Blu-ray players are made by Samsung and will retail at $1,000 (£550) in the US, nearly twice the price of the first HD-DVD players.

Seven discs have gone on sale including classic films like The Terminator.

Even before the players have hit the shelves, backers of the HD-DVD format have upped the stakes.

Toshiba has said it will offer the first HD-DVD recorder in Japan from mid-July 2006.

The recorder will sell for nearly 400,000 Yen (£1,900).

But many people are waiting for what could be the "killer application" for Blu Ray.

Sony's PlayStation 3, which will be launched in mid-November, will come with a Blu-ray drive as standard.

In comparison, owners of Microsoft's Xbox 360, which is already available around the world, will have to buy a separate HD DVD drive when they become available.

Games consoles tend to drive early adoption of technology because hardcore gamers, keen to get their hands on the latest titles, are prepared to buy the latest technology.

The games industry is estimated to be worth $25 billion (£13.5 billion) dollars annually.