Sony has announced two DVD+/-RW drives supporting the new double layer format, one internal and one external drive.

DVD+R DL (double layer) offers almost twice the capacity of conventional writable DVDs, raising it from 4.7GB to 8.5GB. This doubles the recording time from 2 to 4 hours of DVD-quality video, while maintaining compatibility with existing DVD-ROM drives and DVD Video players.

Sony has produced two versions; an internal DRU-700A internal model and an external DRX-700UL model. The external model can be positioned either horizontally of vertically. The internal model is available with white and silver or black front panels.

The DRU-700A and DRX-700UL drives can write to DVD+R DL discs at 2.4x, DVD+/-R at 8x, and DVD+/-RW at 4x. CD-R/RW are at 40x/24x (R/RW), with CD-ROM play at 40x and DVD-ROM play at 12x.

The software bundle with both drives includes the Ahead Nero Burning ROM/Express mastering tool, and applications for DVD authoring, a DVD player and configurable backup software.

Sony claims the drives will be available in May in the UK, pricing yet to be announced. US pricing is $230 (around £130) for the internal drive and $330 (£185) for the external drive.

How does it work?

DVD+R DL (double layer) discs are made from two very thin films of organic dye separated by a transparent spacer layer. Information is recorded by permanent changes in the dye films when they are exposed to the recording head laser. The upper layer is semi-transparent, so the laser can focus through it onto the lower layer, allowing data to be recorded and read back from both layers in turn.

DVD+R DL discs are a write-once media format offering compatibility with DVD-ROM drives and DVD Video players. DVD+R DL compatible drives can also read and write to ordinary single layer DVD discs.