DVD-RAM

DVD-RAM ( DVD-Random Access Memory or general-purpose numerical Disc to chance access ) is a specification of disc presented in 1996 by the forum: DVD Forum . This specification defines the rewriteable media of DVD-RAM and the recorders appropriés.
The DVD-RAM are employed in computers as well as personal video cameras and video tape recorders since 1998.

Introduction

DVD-RAM is a format of rewriteable DVD, as well as the DVD+/-RW, whose principal asset is that it makes it possible to connect readings and writings by chance.

Among three concurrent current technologies of rewriteable DVD (DVD-RAM, DVD+RW and DVD-RW), the DVD-RAM is regarded as a strongly reliable format, because the discs have an integrated control of error and a management system of defect. Consequently, a DVD-RAM is perceived as being better than other technologies of DVD for a use in traditional data-processing tasks like data storage in general, the copy of help and filing, although the standard of Mount Rainier for DVD+RW moderates this slightly. Curiously, the DVD-RAM has a greater presence in the video cameras and the apparatuses of living room (recording) that in the computers.

Principle

The structure of disc of the DVD-RAM is connected with that of the hard drives and to the technology of the diskettes, because the data are stored in concentric tracks. The DVD-RAM can be then consulted like any diskette or hard drive without special software (with the proviso of having an adequate reader).
On the other hand, for the DVD-RW and DVD+RW, the data is stored in only one long track in spiral and requires the use of a special software of the read/write per packages for reading and writing discs of data. A false commonly widespread idea stipulates that a DVD-RAM employs magneto-optical technologies (MONTH). In fact, the DVD-RAM uses a pure medium with phase shift, similar to those of the CD-RW or DVD-RW.
See also the DVD, Compact disk.

Such a disc in addition supports some 100.000 cycles of writing/rewriting, instead of the 1000 cycles supported by a DVD-RW. These optical disks can be read again only by one reader of DVD of fourth generation, or by another engraver of DVD-RAM.

They can contain up to 9,4 Go for the models doubles face (or 4,7 for the models simple face), and were usually contained in a protective cartridge.

Its format by defect is the UDF. It requires pilot then to be used. But it can be reformaté in FAT32 and be then used, under Windows (starting from version XP), Mac OS (starting from version 8.6) and Linux, like a removable hard drive of 4,7 Go as a native. Under Linux it can also be formatted in Ext2, but is not then readable any more under Windows.

Specifications

Since the International Conference Funkausstellung Berlin the 2003 specifications are launched on the market by the group of promotion RAM Promotion Group (RAMPRG), founded by Hitachi, Toshiba, Maxell, LG Electronics, Matsushita/Panasonic, Samsung and Teac. The specifications distinguish 2 versions:
  • DVD-RAM 1.0
    • Simple face, simple layer, with a capacity of 2.58 GB
    • Double face, simple layer, with a capacity of 5.16 GB
  • DVD-RAM 2.0
    • Simple face, simple layer, with a capacity of 4.7 GB
    • Double face, simple layer, with a capacity of 9.4 GB

There exist also DVD-RAM of a capacity of 1.46 Go for a disc with simple face, but they are rare and physically smaller (80 millimetres diameter).

At the origin the DVD-RAM (discs of the type 1.0) were only sold in protective cartridges; the recent recorders of DVD also function with discs without cartridge - some devices do not support any more the cartouches of the whole. Thus several models of engravers DVD for PC are now multi-format. They can thus read and also engrave the DVD-RAM without cartridges of protection.

A disc with cartridge is approximately 50% expensive than a disc without cartridge.

The fact that the first DVD-RAM were sold in cartridges and required readers adapted, different from simple readers DVD from living room or traditional engravers PC, played certainly against this standard, the users preferring less expensive discs DVD+/-RW, simpler to use, and compatible with their computer material and audio-visual.

See too

  • DVD+/-RW, two other principal formats of rewriteable DVD

  • DVD
  • DVD-ROM
  • CD

External bonds

  • Understanding Recordable & Rewritable DVD by Hugh Bennett

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