All about DVD Part 2: The Mess With Formats
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.
In this article we will try and help users to get familiar with
this mess.
DVD-ROM
(DVD Read Only Memory). Generic factory-printed DVD. All
mass-production DVDs with movies, software etc are printed on
DVD-ROM.
DVD-R
(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-Forumas 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-Forumformats, namely
DVD-RW and DVD-RAM.
DVD-RW
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 < b>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.
Early models of DVD-drives required DVD-RW to be
finalized in order to read it properly; however, with the
appearance of new drives this is not necessary anymore in most
cases. It is also not necessary to write at least 1 GB on a
disk. Files of any size, no matter how small can be recorded
now.
Dual layer DVD-RW, called DVD-RW DL with capacity
up to 8.54GB of data is about to appear soon. Currently it is
being developed by Ricoh; unfortunately, it won't be compatible
with current DVD-drives and for this reason is unlikely to ever
become popular. Besides, high capacity Blue-Ray and HD DVD are
also coming soon.
DVD+RW
Despite the decision of DVDForum, DVD+RW (DVD
ReWritable, pronounced as DVD plus R) format was founded and
promoted by coalition of developers called DVD+RW Alliance. First
version of DVD+RW, presented in 1997, was able to hold
only 2.8 GB of data (compared with 4.7 for DVD-RW). These disks
also weren't compatible with normal DVD players and, basically,
all of these were the reasons for DVD Forum not to accept this
standard.
later developers managed to improve both flaws but even after
this, DVD+RW didn't become a standard. As a result,
DVD+RW can only reviewed a potential alternative to
DVD-RW. However, DVD+RW is not without some pleasant
features that DVD-RW misses:
1. Lossless linking technology allows editing of the recorded
disk on sector level, which means that, unlike in DVD-RW, there
is no need to rewrite whole disk when only certain parts of it
needs to be changed.
2. DVD+RW format has better facility for error
handling. If certain sector wasn't recorded properly, it is
rewritten again, more carefully. Also during the process of disk
creation DVD Burner is able to determine the address of sector
that is being recorded, so if the record process is interrupted,
it is possible to resume it from the same position where it
stopped.
3. DVD+RW format supports EasyWrite(Mt. Rainier)
technology, which in conjunction with special software such as
DirectCD or InCD allows using DVD+RW medium as a normal floppy
or hard drive via Explorer or other file manager. The support
for EasyWrite also will be included in new Microsoft Windows
Vista as a standard option.
4. In addition to everything above, maximum writing speed for
DVD+RW is about twice faster than for DVD-RW.
However, DVD+RW format also has some drawbacks.For
example, DVD+RW is less compatible compared to DVD-RW, and the
probability of running into incompatible DVD drive is higher, no
matter what the press-releases and advertisements claim.
Compatibility becomes even bigger issue for old DVD drives.
DVD+RW and DVD+R have a special protection system
designed for them, called VCPS (Video Content
Protection System for DVD+R/+RW). It has all the features of
CPRM (which is for DVD-R\RW) and also supports limitations in
copying of protected digital broadcasts. However, such
innovations are usually welcomed only by movie and video
producers and generally provide only nuisance for users.
DVD+R
Although it might seem strange, DVD+R was introduced by
the same DVD+RWAlliance later
than DVD+RW, namely in 2002, which is the reason why it is
possible to encounter DVD drives that can work with DVD+RW but
are totally incompatible with DVD+R. The introduction of
DVD+R was more of a step back for the developers, as the
only thing they have to do to create DVD+R is to change
the substance in reflective layer of DVD+RW from rewritable to
the one that support only one cycle of writing. Due to this,
DVD+R is actually missing some of useful features of
DVD+RW, such as improved error handling. There is also dual
layer version of DVD+R, called DVD+R DL or
DVD+R9 (actually, it appeared earlier thanDVD-R9). In
general, DVD+R does not differ much from DVD-R.
DVD-RAM
Initially DVD-RAM (DVD-Random Access Memory) was
developed for back-up storage, but later it's capabilities in
handling video became evident, so now there are many home
DVD-RAM camcorders and DVD-RAM recorders which are
aimed to replace VHS.
Although DVD-RAM format was developed by Panasonic in
compliance with DVD Forum, it is much different from DVD-R and
DVD-RW. The chemical part of the process is essentially the same
as in DVD-RW, but the logical part more resembles the operation
of hard disk drive. From the very beginning DVD-RAM is
divided into several sectors. Data is recorded not in circular
track as in normal DVD and CD but is directed in certain sector,
without particular order. During reading of the disk this allows
to find the desired file fast and easily by addressing
appropriate sector. Besides, this layout allows reading and
writing information simultaneously. Interestingly enough,
DVD-RAM does not require any special software for
recording; it can be accessed in the same manner as normal hard
drive or floppy disk.
Although DVD-RAM can withstand more writing cycles (about
100000) than DVD-RW, it is substantially more fragile and have
to be handled with much greater care. For this reason many
DVD-RAMs are being sold in special cartridges, however,
if disk is single-sided, it can be removed from cartridge
temporarily as some DVD-RAM recorders have normal CD tray
instead of cartridge loader.
Some DVD-RAM disks are actually sold without any case at
all. These disks require extreme caution during use.
However, despite being extremely fragile, DVD-RAM has
most reliable error checking. If error is discovered during
burning process, data is simply recorder in different sector;
while in any other DVD format disk will become completely
unreadable.
Speaking of compatibility, any DVD-RAM recorder will have
no troubles reading DVD-R and DVD-RW formats. However, only few
drives will be able to read DVD-RAM format.
Unfortunately, DVD-RAM is much less common compared to
other formats of recordable DVD's and therefore the price for
both drives and disks is still relatively high.
DVD+VR, DVD-VR
DVDs can be recorded in two modes - Video Format and
Video Recording Format (DVD-VR). First one is
compliant with DVD-Video standard and is compatible with any
equipment (this format is used for factory DVD-Video disks and
for video data on DVD-R). DVD-RV mode can be altered
after recording and does not require copy to hard drive in order
to edit disk contents. It is possible to add, cut and delete
video data for the disks written in DVD-VR mode, it is
also possible to add more chapters or change menu. This can be
done for both DVD-RW and DVD-RAM (for DVD-RAM it is actually the
only available mode).
For DVD+RW there exists slightly better version of DVD-VR
called DVD+VR. Some of the positive differences from
DVD-VR are the possibility of creation of full-fledged
menus up to 30megabytes in size, while DVD-VR can only
generate standard play-lists. It is also possible to delete data
from DVD+VR anytime, while in DVD-VR it has to be
done only prior to recording of new data. And the most important
thing - DVD-VR disks can only be played on DVD Burner or
home DVD Recorder, while DVD+VR can be viewed on any
device capable of reading DVD+RW.
Not long ago the selection of preferred format was an important
question, as after selecting, for example, DVD-R compatible
device the user have to live with the fact that the device won't
be able to read or write DVD+R. It was also dangerous to use
DVD-RW or DVD+RW as a floppy to transfer data, because, unlike
CD-RW, there was a chance that there will be incompatible drive
in other computer.
Luckily enough, these problems are now gone.
Summary
After the appearance of first multi-format device on the market,
any modern DVD drive now supports almost all of available
formats, and the selection of desired type of DVD can be made
several times a day, depending on particular task. The only sad
thing that the mess with DVD formats was sorted too late, as
completely new formats of disks are already emerging.