DVD formats at a glance

We know it's confusing so here's an at a glance guide to the four competing recordable DVD formats:


The second version of DVD-RAM, which has been ratified by the DVD Forum, has a capacity of 4.7Gbytes. This format, supported by Panasonic, is at a disadvantage as double sided discs come in sealed cartridges. Single sided discs can come in open cartridges, but can only be written while in the cartridge.


This is backed mainly by Sony but also has the support of Philips and Hewlett-Packard. It has not been ratified by the DVD Forum, and is effectively a direct competitor to DVD RAM. Reflectivity differences, among other problems, mean that the disc can't be read by read by DVD-Video players. It has a capacity of 2.8Gbytes, with upgrade to 4.7Gbytes by 2001 expected.


Developed by Pioneer, this phase-change format is based on DVD-R and can be rewritten around 1000 times. Pioneer plan to make the format compatible for playback with DVD-Video. It offers up to six hours of recording time and has a 4.7Gbyte capacity. It uses groove recording with the address information on land areas for synchronisation at write time.


A write-once standard with limited applications, unlikely to be economic for end users. Useful for organisations which do a lot of archiving or need to store huge amounts of data that won't need to be altered. Possibly useful for games developers. Currently drives are prohibitively expensive at around £5000. Like CD-R, the format uses organic dye polymer. Capacity is 4.7Gbytes.