DVD-RAM (DVDRandom 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.
The term DVD-RAM is a misnomer based on the false assumption that RAM means the opposite of ROM (Read Only Memory). However, RAM stands for Random Access Memory (integrated circuit) and DVD s can inherently not use the random access method.
Compared with other writeable 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 plus R, DVD-R, DVD plus 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.
= Specification =
Since the Internationale Funkausstellung Berlin 2003 the specification is being marketed by the RAM Promotion Group (RAMPRG), built by Hitachi, Ltd., 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 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-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; MS Windows requires a special DVDRAM driver or InCD program, although Windows XP can write to FAT32 formatted discs directly.
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 video recorders, DVD-RAM can be written to and watched (even separate programs) at the same time, much like TiVo.
=== 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.
=See also=
DVD
MultiLevel Recording
Phase-change Dual
= External links =
[http://www.osta.org/technology/dvdqa/ Understanding Recordable & Rewritable DVD]
[http://www.ramprg.com RAM Promotion Group (RAMPRG)] General information.
[http://www.dvddemystified.com/dvdfaq.html DVD Frequently Asked Questions (and Answers)]
[http://www.ecma-international.org/publications/standards/Ecma-331.htm Standard ECMA-331] Defines the 9 cartridge types for 120 mm and 80 mm discs.
