What Is DVD-RAM ???

DVD-RAM (DVD–Random Access Memory) is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD writers. DVD-RAM media have been used in computers as well as camcorders and personal video recorders since 1998. The direct successor of this format will be HD DVD-RAM.

Currently there are three competing technologies for rewritable DVDs: DVD-RAM, DVD+RW and DVD-RW. DVD-RAM is considered a highly reliable format, as the discs have built-in error control and a defect management system. Therefore, DVD-RAM is perceived to be better than the other DVD technologies for traditional computer usage tasks such as general data storage, backup and archival, though the Mt. Rainier standard for DVD+RW somewhat lessens the DVD-RAM format's perceived advantage. Curiously, DVD-RAM has a larger presence in camcorders and set-top boxes than in computers, although the DVD-RAM's popularity in these devices can be explained by the fact that it is very easily written to and erased, which for example allows extensive in-camera editing.

The on-disc structure of DVD-RAMs is closely related to hard disk and floppy disk technology, as it stores data in concentric tracks. DVD-RAMs can be accessed just like a hard or floppy disk and usually without any special software. DVD-RWs and DVD+RWs, on the other hand, store data in one long spiral track and require special packet reading/writing software to read and write data discs. It is a common misconception that DVD-RAM uses magneto-optical (MO) technologies, since both DVD-RAM and MO have numerous rectangles on the disc surface. However, DVD-RAM is a pure phase change medium, similar to CD-RW or DVD-RW.

Since the Internationale Funkausstellung Berlin 2003 the specification is being marketed by the RAM Promotion Group (RAMPRG), built by Hitachi, Toshiba, Maxell, LG Electronics, Matsushita/Panasonic, Samsung and Teac.

The specification distinguishes between

• DVD-RAM version 1.0, recording speed 1x
  • Single-sided, one layer discs with a capacity of 2.58 GB
  • Double-sided one layer discs with a capacity of 5.16 GB
• DVD-RAM version 2.0, recording speed 2x
  • Single-sided, one layer discs with a capacity of 4.7 GB
  • Double-sided one layer discs with a capacity of 9.4 GB
• DVD-RAM version 2.1/Revision 1.0, recording speed 3x
• DVD-RAM version 2.2/Revision 2.0, recording speed 5x
• DVD-RAM version 2.3/Revision 3.0, recording speed 6x max
• DVD-RAM version 2.4/Revision 4.0, recording speed 8x max
• DVD-RAM version 2.5/Revision 5.0, recording speed 12x max
• DVD-RAM version 2.6/Revision 6.0, recording speed 16x max

Physically smaller, 80 mm in diameter, DVD-RAM discs also exist with a capacity of 1.46 GB for a single-sided disc, but they are uncommon. DVD-RAMs were originally solely sold in cartridges; recent DVD recorders however also work with no-cartridge discs — some devices even do not support cartridges anymore. A cartridge disc is about 50% more expensive than a disc without a cartridge.

info : wikipedia