The trickle of drives and media supporting new dual-layer DVD formats looks set to turn into a flood in the coming months as Taiwan's major drive and disc manufacturers prepare to start mass production.

Dual-layer discs feature a second recording layer inside the disc and increase storage capacity to 8.5GB from the 4.7GB storage capacity of a single-layer disc. They are different from double-sided discs because both recording layers can be accessed from one side of the disc � so users don't have to take out the disc and flip it over to get access to the extra capacity. Drives and discs supporting dual-layer versions of both the DVD-R and DVD+R formats were on show by many major vendors at the Computex trade show here this week, with product plans for the latter of the two formats clearly more advanced.

DVD+R DL (dual layer) discs were on display by a number of companies including Ritek, Prodisc Technology, CMC Magnetics and BenQ and the companies were all saying they will start mass production during the third quarter. "We'll be starting disc mass production for the DVD+R DL on June 20," said Vincent Lee product marketing director for disc-maker Ritek. "We are demonstrating a DVD-R DL prototype and have no production schedule because they are still working on the specification."

The products on show at Computex aren't the first to support the DVD+R DL format. Sony, which helped develop the format, has already put a drive on-sale and Mitsubishi Kagaku Media (better known by its Verbatim brand-name in some market) recently began selling the first blank media for the format.

Ritek's Lee said the company is expecting to sell its first discs for a premium of around 75 per cent over single-sided discs and thinks that will fall over time to a premium of around 50 per cent.