DVD-RAM

Optical discs
General Optical disc Optical disc drive Optical disc authoring Authoring software Recording technologies Recording modes Packet writing
Optical media types Compact Disc (CD): CD-DA, CD-ROM, CD-R, CD-RW, 5.1 Music Disc, Super Audio CD (SACD), Photo CD, CD Video (CDV), Video CD (VCD), Super Video CD (SVCD), CD+G, CD-Text, CD-ROM XA, CD-i DVD: DVD-R, DVD+R, DVD-R DL, DVD+R DL, DVD-R DS, DVD+R DS, DVD-RW, DVD+RW, DVD-RAM, DVD-D, DVD-A, HVD, EcoDisc Blu-ray Disc (BD): BD-R & BD-RE Universal Media Disc (UMD) Enhanced Versatile Disc (EVD) Forward Versatile Disc (FVD) Holographic Versatile Disc (HVD) China Blue High-definition Disc (CBHD) HD DVD: HD DVD-R, HD DVD-RW, HD DVD-RAM High definition Versatile Multilayer Disc (HD VMD) VCDHD GD-ROM MiniDisc: MD, Hi-MD Laserdisc: LD, LD-ROM Video Single Disc (VSD) Ultra Density Optical (UDO) Stacked Volumetric Optical Disk (SVOD) Five dimensional disc (5D DVD) Nintendo optical disc (NOD) Archival Disc
Standards SFF ATAPI/MMC Mount Rainier (packet writing) Mount Fuji (layer jump recording) Rainbow Books File systems ISO 9660 Joliet Romeo Rock Ridge / SUSP El Torito Apple ISO 9660 Extensions Universal Disk Format (UDF) ISO 13490
See also History of optical storage media High definition optical disc format war

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.

Design

DVD-RAM was one of three competing technologies for rewritable DVDs. Its competitors are DVD-RW and DVD+RW. DVD-RAM technology provides good data integrity, data retention and damage protection through a number of mechanisms and properties. Therefore, DVD-RAM is perceived by people (who need to store their data on DVDs for long periods of time) to be better than the other DVD technologies for traditional computer usage tasks such as general data storage, and especially data backup and archival. The Mount Rainier Format standard and SecurDisc for DVD±RW (which also works on DVD-RAM, CD-R, and CD-RW) somewhat lessens the DVD-RAM format's perceived advantage in the data integrity category, but not in the data retention or damage protection categories.

DVD-RAM has a larger presence in camcorders and set-top boxes than in computers, although the popularity of DVD-RAM in these devices can be explained by its being very easily written to and erased, which for example allows extensive in-camera editing.

The on-disc structure of DVD-RAM 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. Like magneto-optical (MO) technologies, DVD-RAM has numerous rectangles on the disc surface that define the boundaries of data sectors. However, DVD-RAM is not MO but a phase transition medium, similar to CD-RW, DVD-RW, or DVD+RW.

Cartridge types

Size	Bare disc		Non-removable cartridge		Removable cartridge		Empty cartridge/no disc
sides	single	double	single	double	single	double	single	double
12 cm	yes (type 0)	none	type 1	type 1	type 2	type 4	type 3	type 5
8 cm	yes (type 0)	none	none	none	type 7	type 6	type 9	type 8

Specification

A DVD-RAM disc can be identified by many small rectangles distributed on the surface of the data carrier

These rectangles constitute the hard (factory originated) sectoring of the DVD-RAM

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, Lite-On 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 and 2.8 GB for a double-sided disk, but they are uncommon. DVD-RAMs were originally solely sold in cartridges; recent DVD recorders can work with discs either with or without a cartridge, and many devices do not work with cartridges. Discs can be removed from cartridges for use with these drives (except with type 1 media, see table above).

Compatibility

A DVD-RAM Type 2

Many operating systems like Mac OS (from Mac OS 8.6 up), Linux and Microsoft Windows XP can use DVD-RAM directly, while earlier versions of Windows require separate device drivers or the program InCD.

Windows XP Home and Professional can only write directly to FAT32 formatted DVD-RAM discs. For UDF formatted discs, which are considered faster, a third-party UDF file system driver capable of writing or software such as InCD or DLA are required. Windows Vista and later can natively access and write to both FAT32 and UDF formatted DVD-RAM discs using mastered burning method or packet writing. Even though it is possible to use any file system one likes, very few perform well on DVD-RAM. This is because some file systems frequently overwrite data on the disc and the table of contents is contained at the start of the disc. It should also be noted that Windows Vista (and later) implement the CPRM data protection and thus discs formatted under Windows XP (or earlier) have compatibility issues with Vista onwards (and vice versa).

Mac OS up to 9.2 (Mac OS Classic) can read and write HFS, HFS+, FAT, and UDF formatted DVD-RAM discs directly. In Mac OS X (versions 10.0.x through 10.4.x) UDF-formatting of DVD-RAM is no longer supported, instead formatting and writing DVD-RAM is done in HFS+ format.(UDF support was re-implemented in 10.5 Leopard) (HFS and UFS should also be supported on older versions of Mac OS X that retain support for these file systems.)^[1]^[2]

Many DVD standalone players and recorders do not work with DVD-RAM. However, within "RAMPRG" (the DVD-RAM Promotion Group consisting of Hitachi, Toshiba, Maxell, LG Electronics, Matsushita/Panasonic, Samsung, Lite-On, Teac) there are a number of well-known manufacturers of standalone players, recorders, and camcorders that can use DVD-RAM. Panasonic, for instance, has a range of players and recorders which make full use of the advantages of DVD-RAM.

The newest DVD-RAM Specification, DVD-RAM2 (also called RAM2), is not compatible with DVD drives that do not specifically allow reading DVD-RAM2 discs.^[3]

Some high end products such as IBM System p frames require DVD-RAM instead of DVD-RW.^[4]

Advantages

A DVD-RAM for DVD recorders

A miniDVD-RAM with DVD round holder

How to open a DVD-RAM cartridge

Long life — without physical damage, data is retained for an estimated 30 years. For this reason, it is used for archival storage of data.^[5]^[6]
Can be rewritten over 100,000 times for the lowest write speed discs (DVD±RW can be rewritten approx. 1,000 times). Faster DVD-RAMs allow fewer rewrites (3x speed: 100,000, 5x speed: 10,000) , but still more than DVD+RW or DVD-RW. (These are theoretical numbers. In practice they could be smaller depending on the drive, the treatment of the disc and the file system.)
Reliable writing of discs. Verification done in hardware by the drive, so post-write verification by software is unnecessary. Software verification is disabled in all current DVD Video Recorders.
Disc defect management designed to safeguard data.
DVD-burning software may not be required — discs can be used and accessed like a removable hard disk. Mac OS (8.6 or later) uses DVD-RAM directly. Windows XP uses DVD-RAM directly for FAT32-formatted discs only. Windows Vista is able to write directly to both FAT32- and UDF-formatted DVD-RAM discs from within Windows Explorer. Device drivers or other software are needed for earlier versions of Windows.
Very fast access of small files on the disc.
Small 2 KB disc block size wastes less space when writing small files.
Finalization not necessary. For video recording use, other media such as DVD+RW (when used in DVD+VR mode) do not require a separate finalisation either as finalisation is automatic. The table of contents can be overwritten in this latter media.
Media available with or without protective cartridges; can be used in the cartridge by many devices.
In some video recorders DVD-RAM can be written to and read at the same time, allowing one program to be recorded and a different one, or an earlier part of the same one (time slip recording), to be viewed at the same time. DVD+RW recorders can achieve the same thing, and more recently some DVD-RW recorders achieve it as well (though only at the slower recording speeds).
Usable with some high-end security digital video recorders, such as the Tecton Darlex, as a secure and long-lasting export medium.
Holds more data when using Double Sided discs than dual-layer DVD+RW and DVD-RW - 9.4GB for DVD-RAM vs 8.5GB for DVD+RW DL and DVD-RW DL.
Has write-protect tabs to prevent accidental deletion when used in a cartridge.

Disadvantages

High-speed media unavailability: Only 3x discs are readily available.
Higher media cost.
A hazard exists with 16x RAM2 discs in non-RAM2 drives: the disc may be ejected while spinning. Either way it is not a problem of DVD-RAM media, but the drives that do not recognize them properly.
Less compatibility than DVD+RW and DVD-RW, despite predating both formats (as noted above).

References

↑ "Using DVD-RAM discs". support.apple.com. 2012-02-18. Retrieved 2014-02-05.
↑ "Mac OS X: "The disc 'Ram' could not be modified" Alert". support.apple.com. 2012-02-17. Retrieved 2014-02-05.
↑ "Usage Of 16 X DVD-RAM Disc (RAM2 Disc)". Web.archive.org. 2008-01-31. Archived from the original on 2008-01-31. Retrieved 2009-09-28.
↑ "HMC backup". Web.archive.org. Archived from the original on 2007-02-23. Retrieved 2009-09-28.
↑ "Fujifilm DVD-RAM Disc". Fujifilm. 2006-10-17. Archived from the original on 2006-10-17. Retrieved 2009-08-15.
↑ "Update: Phase Change WORM". West World Productions and Gale Group. Retrieved 2007-12-29.

External links

Wikimedia Commons has media related to DVD.

DVD

Discs	DVD MiniDVD DVD card DVD-ROM DVD-RAM DVD-Audio DVD-Video DVD-R DVD-R DS DVD-R DL DVD-RW DVD+R DVD+R DS DVD+R DL DVD+RW Inkjet printable DVD

Technology	UDF DVD region code DVD copy protection CSS HDCP AACS DVD authoring DVD burning DVD ripping DVD recordable DVD program Anamorphic DVD DVD Video OBject DVD-VR DVD+VR DVD±R DVD Multi DVD writing speed DVD emulation DVD rot

Groups	DVD Forum DVD Copy Control Association DVD+RW Alliance DVD club

Hardware/Software/Content	DVD Case VCR/DVD combo DVD player Portable DVD player DVD recorder DVD drive External DVD DVD remote DVD ripper DVD game DVD single DVD magazine DVD documentary Straight to DVD

Court cases	DVD CCA v Bunner DVD CCA v Kaleidescape Real vs DVD CCA DeCSS

Lists	DVD manufacturers DVD recordable manufacturers DVD authoring software DVD burning software DVD copy protection schemes

Variants based on DVD	cDVD SACD DualDisc EVD HVD FVD ML DVD HD/DVD 3× DVD BD-5 BD-9 Nintendo disc Digital Video Express (DIVX) DVD-D

See also	HD DVD Blu-ray Disc LaserDisc CD Video Compact Disc VCD SVCD CD-DA CD-ROM

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