DVD-RAM

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DVD-RAM medium

One of the three rewritable DVD formats is referred to as DVD-RAM , which is said to be distinguished from the other two by its better rewritability and data security . DVD-RAM is used in computers as well as camcorders and hard disk recorders , but is increasingly being replaced by flash memory in these applications .

History and dissemination

Originally there were only pure playback DVDs such as DVD-Video , DVD-Audio and DVD-ROM . In addition, a rewritable DVD format should initially only be available for the computer sector, the DVD-RAM. The "-RAM" stands for " Random Access Memory ". In the meantime, however, DVD-RAM is also being used particularly successfully in other areas such as video.

DVD-RAM is the oldest rewritable DVD format, but it is less common than the other two rewritable DVD variants DVD ‑ RW and DVD + RW. This is due to the fact that the members of the DVD Forum industry association jointly approved it in 1996, but also introduced the DVD-RW and DVD + RW DVD formats out of various market interests . Both competing formats are also based on the phase change technique , but they have some savings that are at the expense of good rewritability and data security. The two DVD variants DVD-RW and DVD + RW are referred to below as DVD ± RW for short.

The first DVD-RAM devices came on the market in 1997. DVD-RAM has been gaining increasing market importance since 2002 because it has established itself as the standard in the DVD video recorder and DVD camcorder sector due to its advantages in easy rewriting and easier handling compared to DVD ± RW. As DVD-RAM has become more widespread, media prices have fallen so that it is now also interesting for use in the consumer sector for backing up computer data. The greater market importance of DVD-RAM in the computer sector can also be seen from the fact that the former self-confessed advocate of DVD-RW, the manufacturer Pioneer , now also offers DVD burners that can process DVD-RAM.

In the computer sector, it is not possible to give an exact indication of the actual distribution of DVD-RAM in use, because since 2004 DVD burners, which can also write DVD-RAM, have only been offered as so-called super multi-burners . A super multi-burner is a device that can handle all DVD formats. These DVD burners have been available at prices similar to good DVD ± RW burners (without DVD-RAM) since 2004 and their technical performance data also impress customers who use the DVD burner exclusively for DVD ± R and DVD ± RW. The clearest feature of this situation is that some dealers sell DVD-RAM-compatible burners, but only offer blank DVD ± R and DVD ± RW media and not DVD-RAM media.

This situation has arisen because the manufacturers of DVD-RAM devices hardly do any publicity for the DVD-RAM. For example, there are usually no explanatory descriptions on the manufacturers' websites about the advantages of DVD-RAM. Such representations are also missing in the instructions for the devices. DVD-RAM is therefore only used by insiders in the computer sector, although it allows much greater data security and easier handling than a DVD ± RW.

Intended successor

Theoretically, it would be possible to equip the DVD-RAM with multiple layers in addition to the currently possible use on both sides - similar to the DVD ± R dual layer or double layer. However, this option has been abandoned in order to concentrate more on the so-called next generation of optical media. For DVD-RAM there was also the designated successor HD DVD-RAM of the HD-DVD group. The capacity of this medium should be around 20 GB for single-layer discs and around 32 GB for double-layer discs. The basic properties of the DVD-RAM were retained. In general, HD-DVD drives are backwards compatible with DVD-RAM, i. H. the DVD-RAM storage media can continue to be used directly without copying. However, the development of HD-DVD devices with HD-DVD-RAM support has ended due to the abandonment in the format dispute with the Blu-ray Disc . In contrast to HD DVD, the Blu-ray consortium does not provide a counterpart, even if the use of UDF version 2.5 or higher as the file system should allow BD-RE to be integrated as removable disks (as a software implementation).

Differences between DVD-RAM and DVD-RW and DVD + RW

A DVD-RAM can be distinguished from other DVD formats with the naked eye thanks to its typical small sectoring rectangles that are scattered on the recordable side . Sectoring serves to increase data security.
Enlargement of the sectoring rectangles.

In addition to DVD-RAM, there are two other rewritable DVD formats, DVD-RW and DVD + RW. Despite the similar appearance, name and capacity, the differences are serious. In general terms, the main difference between DVD ± RW and DVD-RAM is that DVD ± RW is designed for maximum compatibility with DVD-Video and DVD-ROM, while DVD-RAM is optimized for data security . The differences in detail:

Interchangeability
DVD devices can usually play a DVD ± RW, while this is not the norm with DVD-RAM and mostly only with higher-quality DVD devices - compare chapter Device types, manufacturers and RAMPRG .
Sectoring
With the naked eye, DVD-RAM media can be clearly distinguished from other DVD variants based on their sectoring, which visually appears as many small scattered rectangles on the back of a DVD-RAM (compare the first illustration above). Sectoring serves, among other things, for higher data security.
formatting
In contrast to a DVD ± RW, DVD-RAMs are often formatted at the factory. In addition, a DVD-RAM can be reformatted in a few seconds thanks to its sectoring, in contrast to DVD ± RW.
Defect management
The DVD ± RW has no defect management. The DVD-RAM, on the other hand, has the same tried and tested defect management as a hard disk: If a storage location ( sector ) on the DVD-RAM cannot be written to, this location is marked as defective and the content is saved elsewhere. The defect management of the DVD-RAM is very reliable because it is done by the drive electronics, like with the hard drive. For DVD ± RW, the software manufacturers of burner programs only offer a makeshift solution for the lack of defect management. After burning a DVD ± RW, an optional read check for unnoticed burning errors takes place. The subsequent verification of the DVD ± RW is a workaround because in the event of an error the error cannot be corrected, the DVD ± RW medium has to be thrown away and all contents have to be burned on a new DVD ± RW medium. The defect management of the DVD-RAM can also be called “automated verification with error correction” because it takes place during the burning process.
speed
DVD-RAM media writes about 50 percent slower than DVD ± RW media. This speed difference only exists when viewed superficially. If the necessary subsequent verification is added at the time of burning a DVD ± RW, the total time is roughly the same, but without the advantages of defect management of a DVD-RAM (see above).
Very low system load
Even if the manufacturer's specifications for DVD-RAM burners for computers always require PCs with high processor performance, this information always relates to the multimedia software supplied (for example for playing videos). The DVD-RAM burner itself does not make any special demands on the hardware. Regardless of the load on the CPU or the hard drive of the computer, no burn errors can occur in the drive electronics of the DVD-RAM burner due to the defect management (see above). A DVD-RAM is therefore particularly suitable for data backups that are to be created at the same time.
Access similar to a removable hard drive / floppy disk
While DVD ± RW in conventional format can only be written to with a burning program, with DVD-RAM, after installing the DVD-RAM driver, individual files can be written or deleted directly from the file manager (e.g. Explorer) or other applications. renamed or moved. When formatting the DVD-RAM with FAT32 and UDF 2.01, the burner works like a hard disk. Files can be copied or dragged and dropped onto the open medium and are written immediately. However, DVD ± RW discs can also be used with Mount Rainier .
lifespan
The DVD-RAM is said to have a longer lifespan than the DVD + R and DVD-R media because no organic layers are used. Germanium , antimony and tellurium (GeSbTe) are used as materials for 1x, 2x and 3x media or a bismuth coupling material (BCM) for 5x and 16x media instead of the silver used for DVD-RWs , Indium , antimony and tellurium (AgInSbTe). In order to avoid scratches on the surface for a long time, the DVD-RAM is also available in a cartridge version right from the start (see below). The industry advocates a lifespan of 30 years, although this is not specified in any officially binding guidelines and has not yet been proven by any independent study. The c't magazine writes : "In all of Europe there is no independent laboratory that could test the quality of DVD-RAMs."
Rewritability
The DVD-RAM, which can be changed around 100,000 times (applies to 2x and 3x DVD-RAM), can be rewritten almost any number of times. On the other hand, a DVD ± RW can at best be rewritten 1,000 times, in practice, depending on the combination of burner and medium, it is often significantly less than that. It should be noted that DVD-RAM media can only be written to about 10,000 times at speeds of 5x and more because the chemical structure is different. If the UDF file system is used, the DVD-RAM also achieves the specified rewritability, because individual sectors that can no longer be rewritten can also be corrected in the directory system (in contrast to a DVD ± RW).
Write / read strategy
The DVD-RAM is the only DVD that can be read and written at the same time. For example, it is possible to use a DVD-RAM recorder, which is connected to the television at home instead of a video recorder, to watch the program that has been running for some time from the start, while the recorder continues to record the program. Otherwise this is only possible with recorders with integrated hard drives. The DVD-RAM recorder is considerably cheaper in comparison.

Differences between DVD-RAM and MO disk

An open MO that shows the same sectoring as the DVD-RAM.

In the literature, the DVD-RAM is often mistakenly viewed as an MO variant because the sectoring on the data carrier surface is visible in both of them (compare the first and second figures; especially when enlarged). Sectoring is used to improve reading and writing accuracy. Sectoring can, however, be used in various techniques: DVD-RAM uses phase-change technology as a reading and writing method , while MO disk uses magneto-optical technology . For further differences between the DVD-RAM and the MO disk, see the keyword Magneto Optical Disk .

Differences between DVD-RAM and DVD-Video

A DVD-RAM can be used like a DVD-Video , so videos can also be stored on it and equipped with a DVD menu. On DVD players that can also read DVD-RAM, these can also be played without any problems.

There are differences when videos are written to DVD-RAM using a DVD video recorder rather than a PC. Specifically: A DVD-RAM recorded on a DVD video recorder cannot be copied to a DVD ± R or DVD ± RW directly on the PC and then used on any DVD player because the video file must first be converted.

The DVD-RAM video recorders initially use a different directory structure . If the videos of the DVD-Video are in the directory (as with DVD ± R and DVD ± RW) VIDEO_TS, this directory is on the other hand with DVD-RAM DVD_RTAV. Second, the file format used for the video data is different . The video is not saved in the VOB file format , but in VRO (Video Recording Object). The VRO file format allows for better recording and video editing, but it is not compatible with classic DVD players. Current DVD player software for the PC such as WinDVD or PowerDVD can now play DVD-RAM video files directly without conversion. In 2004 there was not a single DVD-VCR with DVD-RAM which, at the request of the user, could generate VOB files directly so that they can be converted into a DVD ± R by simple PC copying. With some recorders you can now choose the recording format.

Specification of the media

Knowing about the specification of the media is useful when evaluating DVD-RAM technology and purchasing DVD-RAM devices and media. Only information that is of general interest is presented below.

The DVD-RAM media are available in two different diameters: one with a CD diameter of 120 mm and one with a mini CD diameter of 80 mm. First, the specification of the typical DVD-RAM based on storage capacity , equipment, write protection and file system will be dealt with.

a) The classic DVD-RAM with a diameter of 120 mm
  1. Storage capacity: The classic DVD-RAM medium (120 mm diameter) is available in different storage capacities. Most current devices can no longer process DVD-RAM 1.0.
    • DVD-RAM version 1.0 :
      • single-sided media with one layer and a capacity of 2.40 GB
      • double-sided medium with one layer each and a total capacity of 4.81 GB
    • DVD-RAM version 2.0 :
      • single-sided media with one layer and a capacity of 4.38 GB
      • double-sided medium with one layer each and a total capacity of 8.75 GB
      • Speed ​​2x
      • Revision 1.0: speed 3x
      • Revision 2.0: speed 5x
      • Revision 3.0: speed 6x max
      • Revision 4.0: speed 8x max
      • Revision 5.0: speed 12x max
      • Revision 6.0: speed 16x max
  3. Format class for speed: The DVD-RAM media are designed for different write and read speeds.
    • Class 0: speeds from 2x to 5x. This is the original format class. These media can be read and written to by Class 0 and Class 1 devices. The phase change material used for the 1x, 2x and 3x media is germanium, antimony and tellurium (GeSbTe), the color is golden brown. 5x media are made of the same material as Class 1 media, which results in a reduction in write cycles (see Class 1). In the meantime (as of February 2008), however, DVD-RAM with a speed of 5x are also available, which are designed for a number of write cycles of up to 100,000 (color golden brown, i.e. GeSbTe as phase change material).
    • Class 1: speeds from 8x to 16x. The older Class 0 devices can read this media, but not write to it. A bismuth coupling material (BCM) is used as the phase change material, whereby the writing speed could be increased, but the number of possible write cycles had to be reduced from 100,000 to 10,000. The color of this media is dark green. The introduction of this format class was announced in March 2005 to increase speed. Although drives are now available (February 2007) that support this format class and, according to the manufacturer, can write at up to 12 times the speed, these media have not yet been available (January 5, 2008).
  5. Packaging: The classic DVD-RAM media are available in four different types of packaging, which are numbered here with "Variant I" to "IV" because the manufacturers do not use a uniform terminology. The most common is variant III.
    • Variant I : This DVD-RAM media type was the first to exist. With him, the single or double-sided DVD-RAM is firmly in protective packaging that resembles a 3.5 ″ floppy disk . This packaging is also known as a caddy or cartridge and primarily protects the DVD-RAM against scratches and dirt. The cartridge does not completely protect against sunlight and dust, which is why it can be pushed into the protective cover (made of thin plastic or cardboard) provided for longer storage. Variant I is particularly widespread with DVD-RAM video recorders, because here the consumer can touch and put down the DVD-RAM without any worries. The variant I is also known as Type I called.
      Variant II. The red slide switch for write protection is clearly visible.
    • Variant II : As variant I, but the DVD-RAM can be removed from the cartridge if necessary. This is useful because many newer DVD-RAM devices - especially in the computer field - forego the ability to read a DVD-RAM with a cartridge for simpler and therefore cheaper mechanics. This variant therefore offers the best protection with maximum flexibility at the same time. The variant II is also called Type 4 .
    • Variant III : With this variant, the DVD medium is delivered in a simple jewel case or slim case . With a careful use, the lack of permanent protection of DVD-RAM with a cartridge hardly a problem, similar to that in the known CD-R and DVD ± R is the case. The media of "Variant III" are significantly cheaper than those of Variants I or II. For an additional charge, this version is also available with a scratch-resistant surface to ensure more durability in everyday use.
    • Variant IV : In the meantime, there are also occasional DVD-RAM media in the cakebox , which are a little cheaper in terms of price because they lack the jewel cases or slim cases. It is still unclear to what extent the stacking of the media affects the quality. What is certain is at least that the media should not be stacked again after first use; For maximum data security, they must then be stored individually in protective covers.
  7. Write protection: The following does not mean the typical write protection that the file system provides and that only extends to individual files or directories, but rather the special protection options of a DVD-RAM that apply to the entire DVD-RAM medium. A DVD-RAM medium can be protected against unintentional alteration in three different ways: by operating system or driver (software), by slide switch (medium) and by drive (hardware).
    • Driver: Every DVD-RAM medium has a write protection bit that allows write protection for the entire medium regardless of the file system. This write protection is observed by the drive on the hardware side. Special software or a driver is required to activate or deactivate this write protection bit. In a virus-contaminated environment, the write protection bit offers no protection if the medium is still unprotected and it has to be inserted into a drive for activation. In short: Write protection is more suitable for such cases, which can be activated by hand without the aid of software, such as the slide switch or a special drive.
    • Slide switch: A DVD-RAM medium itself has no mechanical write protection. However, there is a write protection slide switch on the cartridges similar to the 3.5 ″ diskette. Of course, this switch is only effective if the DVD-RAM is used with a cartridge. Most newer drives can often only load a DVD-RAM medium without a cartridge, so that the elegant slide switch does not protect in all cases.
    • Drive, 1: For DVD-RAM media that are only ever used without a cartridge, a very secure and easy-to-use makeshift ad-hoc write protection is to use a second drive that a DVD-RAM can only read can, but not write. This second drive is a DVD-ROM drive that can also read the DVD-RAM DVD format, cf. Chapter on device manufacturers ( see below ).
    • Drive, 2: Since the DVD-RAM is a medium designed for data security, some drives (e.g. Panasonic LF-D201) had a switch that was persistently adjustable in the device firmware, which, according to the factory settings, enabled media without a cartridge (or media removed from it) treated as read-only because of possible contamination. As a user, you can set this setting according to your own needs using special software supplied by the device manufacturer (e.g. Panasonic LF-D201: RAMDiscTool).
  9. File system: A DVD-RAM medium can be formatted in different file systems . The UDF file system is recommended by manufacturers, and some manufacturers also offer DVD-RAM media already formatted with UDF at no extra charge (otherwise UDF formatting takes about a minute). For a detailed presentation of the advantages and disadvantages of the various file systems and tips on additional software and drivers, see the Wikibook DVD-RAM .
  11. Color: The back of the DVD-RAM is always golden-brown for production-related reasons or dark green for high-speed media (see above "Format class for speed"). After writing (not formatting) the DVD-RAM, the changed storage space changes color from golden brown to dark golden brown or dark green to black green.
b) The mini DVD-RAM with 80 mm diameter
A mini DVD-RAM inserted into a U-shaped DVD round holder .
The mini DVD-RAM came out later and is primarily used in camcorders . The mini DVD-RAM allows a smaller and more compact design of a camcorder. DVD camcorders lack space for the usual drawer system for inserting a DVD, which is why the mini-DVD has to be inserted using a so-called "DVD Round Holder" (see illustration on the right). This "DVD Round Holder" is not a cartridge and is therefore packed in a 3.5 ″ cover, which is identical in structure and size to a cover for the MO disk .
In Asia, a mini DVD-RAM is also stored in a mini cartridge.
The mini-DVD-RAM has a storage capacity of 2.6 GB when used on both sides, which is sufficient for a video recording of up to 120 minutes (with lossy compression with MPEG-2 coding ).

Software support

UDF is the most suitable formatting format for DVD-RAM, it is supported by Windows Vista and Windows 7 . A separate driver must be installed on Windows XP and older Microsoft OS (many drives are supplied with InCD from Nero AG ). DVD-RAM can also be used with FAT and NTFS , but errors occur more frequently because deleted blocks are not reliably removed from the TOC .

Device types, manufacturers and RAMPRG

There are four basic types of DVD device: DVD-RAM players, DVD-RAM burners, DVD-RAM camcorders, and DVD-RAM video recorders. For details, see DVD-RAM Wikibook .

The prominent manufacturers of devices and media for DVD-RAM founded the RAM Promotion Group (RAMPRG), which has endeavored since the International Consumer Electronics Fair in 2003 to jointly market DVD-RAM more actively. The RAMPRG included the following manufacturers, among others: Hitachi , JVC , Toshiba , Maxell , LG Electronics , Panasonic ( Matsushita ), Samsung , Verbatim and TEAC . The RAMPRG no longer exists.

Norms and standards

logo

literature

  • Bernd Steinbrink: DVD competition . In: c't . tape 15 , no. 8 , 1998, pp. 160–165 ( heise.de [accessed June 16, 2019] What is noteworthy about this article are the illustrations showing the structure of a DVD-RAM medium).
  • Stephan Becker: Finely burned . In: c't . tape 15 , no. 25 , 1998, pp. 190–195 ( heise.de [accessed on June 16, 2019] The article presents the technical differences between the MO disk and DVD-RAM in an understandable and detailed manner).
  • Hartmut Gieselmann: Satanic discs. DVD burners switch to 18X and connect via SATA . In: c't . tape 23 , no. 8 , 2006, p. 120–123 , info box “DVD-RAM and UDF” on p. 122 ( heise.de [accessed on June 16, 2019] The article describes false reports about InCD).

Web links

Commons : DVD-RAM  - collection of pictures, videos and audio files
Wikibooks: Tips for Using DVD-RAM  - Learning and Teaching Materials

Individual evidence

  1. ↑ Hartmut Gieselmann: Silver memories: archive DVDs in the long-term test. In: c't 2008, No. 16
  2. ↑ Heise-News: DVD-RAM switches to 16X from July , March 31, 2005.
  3. ↑ Homepage of the RAMPRG ( Memento from October 25, 2007 in the Internet Archive )