DVD-RAM
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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 are used in computers as well as camcorders and personal video recorders since 1998.
Compared with other DVDs, DVD-RAM is more closely related to hard disk technology, as it has concentric tracks instead of one long spiral track. Unlike the competing formats DVD+R, DVD-R, DVD+RW and DVD-RW, you do not need special DVD burning software to write or read DVD-RAMs on a computer. DVD-RAMs can be accessed like a usual floppy disk or hard drive.
See also DVD, Compact Disc.
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Specification
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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. DVD-RAM is considered a highly reliable format, as the discs have built-in error control. It is a common misconception that DVD-RAM uses magneto-optical (MO) technologies: DVD-RAM is a pure phase change medium.
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The specification separates between
- DVD-RAM 1.0
- 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 2.0
- Single-sided, one layer discs with a capacity of 4.7 GB
- Double-sided one layer discs with a capacity of 9.4 GB
Physically smaller DVD-RAM discs also exist with a capacity of 1.46 GB, 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 cartridge.
Comparison
Currently there are three competing formats for rewritable DVDs: DVD-RAM, DVD+RW and DVD-RW.Dvdramopen2.gif
DVD-RAM is more suited to data backups and use in camcorders than DVD±RW.
Advantages of DVD-RAM
- Long durability of minimum 30 years.
- Can be rewritten > 100,000 times (DVD±RW ca. 1,000 times).
- No DVD burning software required in computers – discs can be used and accessed like a removable hard disk; on MS Windows requires special DVDRAM driver or InCD program.
- Very fast access of smaller files on the disc.
- Automatic hardware verification of written data, no need to run a software verification after the burning finished
- The cartridges make it very handy (where applicable).
- In DVD recorders DVD-RAM is the only removable medium which allows time shifting.
Disadvantages of DVD-RAM
- Type 2 discs do not always come in a case.
- Most DVD recorders do not support DVD-RAM.
- The medium is more expensive than DVD±RW.
- DVD+RW can be written faster than DVD-RAM when writing large amounts of data.
External links
- ramprg.com (http://www.ramprg.com) - General information and good animated diagrams.
- DVD Frequently Asked Questions (and Answers) (http://www.dvddemystified.com/dvdfaq.html)
- Standard ECMA-331 (http://www.ecma-international.org/publications/standards/Ecma-331.htm) explains the 9 (!) caddy types, the most common being 1, 2 and 4.de:DVD-RAM