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Basics of recordable DVD discs and drives
As can be expected, many Digital Video enthousiasts are keeping a close look at the development of recordable DVD appearing on the market. DVD players are becoming more an more widespread and the great quality, both in terms of video and audio, will appeal strongly to the majority of our visitors who produce their own movies. If you have been working with VCD or even SVCD you know that both systems have their limitations. Putting movies on DVD sounds like a great idea!
Since recordable DVD has entered the market not too long ago, a number of different systems still exist. And the different names like DVD-RAM, DVD-R, DVD+RW etc. can be somewhat confusing for many. This article describes some basics about the different types of discs and drives and some of their features.
1. Layers, Sides and Sizes.
Recordable DVD's are available Single Sided (SS) and
Double Sided (DS), meaning that both sides can contain
data. To my knowledge there are currently no drives or players
available that can read on both sides, meaning that they have
to flipped over in order to read the other side. Logically,
Double Sided DVD's can contain twice the amount of data compared
to their Single Sided counterpart.
Another distinguishing feature is that they can be either
be Single Layer (SL), Double Layer (DL)
or Mixed Layer (ML). A Double Layer DVD contains
two layers on one side of the disc that each contain data.
Amount of data that can be stored is a little less then twice
the amount of data than a Single Layer DVD. A Mixed Layer
DVD is Double Layer on one side and Single Layer on the other
side.Furthermore there are also two physical sizes in DVD:
the "normal" size of 12 cm and a smaller version
of 8 cm.
Typical capacity of a normal size SS/SL recordable DVD is
4.7 Gbytes (4.7 billion bytes, not Gigabytes). SS/DL is 8.54
Gbytes. The largest one would be DS/DL with a staggering capacity
of 17.08 Gbytes!
2. DVD-R
The first recordable DVD to appear on the market was the DVD-R launched in 1997. Just like CD-R, it is writable and not rewritable. The initial version could contain 3.95 Gbytes, later they were improved to contain up to 4.7 Gbytes. It is suitable both for storage of computer data and for DVD-Video. Initially, discs and drives were aimed at the professional market DVD-R(A), later a consumer version DVD-R(G) was released. The two types are physically different and need different drives for writing. The first DVD writer for DVD-R(G), the Pioneer DVR-A03, entered the market in the spring of 2001. Nice feature of this player is that it also reads and writes DVD-RW. t is not completely clear to me if you can also rewrite DVD-RW with this device. More about this will follow soon...
3. DVD-RAM
DVD-RAM is a rewritable DVD that was introduced in 1998. Major difference between these discs and all other recordable DVD types is that it usually is shipped inside a special cartridge in which it also must be entered into the drive. Although they can be shipped without the cartridge or, in other cases, they can be removed from the cartridge, writing can only be done while the disc is inside the cartridge. The format was developed primary for storage of computer data, not for DVD-Video. The drives that are sold to write DVD-RAM are less expensive in comparison with drives to write DVD-R, but the big disadvantage is the low level of compatibility with other types of drives.
4. DVD-RW
As a logical next step after DVD-R, Pioneer launched the DVD-RW late 1999. Also indicated as DVD-R/W, it is a rewritable format and can be rewritten about 1,000 times. Unlike the DVD-RAM, the physical appearance of these discs is identical to DVD-R. The standard for these discs is based on the DVD-R standard and can be used for both computer data and DVD-Video. The first consumer DVD recorder that entered the market for recording video on DVD-RW made use of another DVD format that is not compliant with exisiting DVD players. Follow on versions of DVD-RW recorders don't have that problem and can also write on DVD-R.
5. DVD+RW
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