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Encyclopedia > DVD RAM
You can recognize a DVD-RAM immediately because visually there are lots of little rectangles distributed on the surface of the data carrier.
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You can recognize a DVD-RAM immediately because visually there are lots of little rectangles distributed on the surface of the data carrier.

DVD-RAM (Digital Versatile Disc –- 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 much more similar to a harddisk, 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.

Contents

Specification

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A DVD-RAM Type 2.

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.


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. DVD-RAM is in particular more suitable for data backups and the use in camcorders than DVD±RW.


Advantages of DVD-RAM compared to the competing formats

  • 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.
  • 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.

Type 2 does not always come in a case.


Disadvantages

  • 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 link

Commons
Wikimedia Commons has multimedia related to:
DVD
  • Official website of the RAM Promotion Group (http://www.ramprg.com)
  • Pansonic article about history of DVD-RAM (1973-1998) (http://www.panasonic.com/industrial/computer/storage/dvdram/about/history.htm).

 
 

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