Getting familiar with recordable DVD formats
Probably everyone nowadays had a need to transfer information between several PC’s or make a backup copy of favorite movie. Recordable DVDs (DVD-Rs) serve this purpose very well, but it could be quite hard to get familiar with all the different types of them. While in CD era there were only two formats, namely CD-R for recordable and CD-RW for rewritable disk, for DVD it is not that simple. The fight between manufacturers to enforce their own formats led to the mess of the biblical scale. Besides DVD-R and DVD-RW, in most shops it is possible to encounter DVD+R, DVD+RW and even mysterious DVD-RAM. And there is no guarantee that your DVD drive will be able to work with newly purchased disk.Have a look at trading tickers dvd for more info on this.
In this article we will try and help users to get familiar with this mess.
(DVD Read Only Memory). Generic factory-printed DVD. All mass-production DVDs with movies, software etc are printed on DVD-ROM.
(DVD-Recordable – pronounced as “DVD Are” or “DVD Dash Are”). This is the first format for recordable DVDs. It was developed in 1995 by Pioneer and was approved by DVD-Forum as a main standard for recordable DVD. Basically, this formatis direct analogue of CD-R but with bigger capacity and, respectively, smaller track size. As with CD-R, record is made by altering the structure of organic polymer in reflective layer with powerful laser. DVD-R can be recorded only once, but it is compatible with most DVD players and computer DVD drives. Properly stored and unscratched DVD is believed to remain readable for hundreds of years.
Initially DVD-R was only single-layered, but recently double-layer DVD-R DL (dual layer) becomes available. They are also known as DVD-R9, however, they are still uncommon and they can be recorded only on newest models of DVD burners. Trying to record these disks in non-compatible drive can actually lead to the DVD burner damage.
There are two types of DVD-R disks: DVD-R Authoring (DVD-R (A)) and DVD-R General (DVD-R (G)).DVD-R (A) type of disks appears first and was used only for professional needs. This type of disk allows recording of anything, including hidden area and keys, which means that It can be used as a master-copy for mass-production.
Devices and disks compatible with DVD-R(A) are professional equipment and therefore very expensive and uncommon.
DVD-R General (G) is much more common. It was developed later specifically for the needs of common users. This type of disks does not allow making a full copy of protected DVD – no keys will be recorded and resulting disk simply will not play. On the other hand, there are lots of devices and blank DVD-R son the market for this type of disks, and they also quite inexpensive. DVD-R (G) devices can read DVD-R (A) disks but cannot record anything on them.
Unlike CD-R, DVD-R shave a special copy protection called CPRM, which stands for Content Protection for Recordable Media. Each blank DVD-R has inerasable encrypted entry (lead in) in hidden area of the disk, which contains information about type of medium and manufacturer. When backup copy of protected DVD is made, copy program will re-encode the information again, but this time using this hidden information, so twill not be possible to copy the resulting disk again as it will require hidden information from specific medium. This type of copy protection also supported by other DVD-Forum formats, namely DVD-RW and DVD-RAM.
DVD-RW (DVD ReWritable) was also developed by the Pioneer and essentially is the same DVD-R with only difference that reflective layer’s state can be transformed by the laser more than once. The specifications for DVD-RW states that each DVD-RW medium should withstand up to 1000 rewriting cycles. The reflectivity of DVD-RWs is much less then of DVD-R and some DVD drives can mistake them for dual-layer DVD. For this reason DVD-RW are compatible with only approximately 70% of existing DVD players.