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DVD-R
versus DLT for DVD Replication
Stephen Clark Jr.
January 4, 2001
Making a glass master from a DVD Rom is only doable if it hasn't been endcoded
with CSS.
Digital Linear Tape (DLT) has, for some time, been the de facto standard
as an input medium for DVD mastering and replication. DLT's capacity and
reliability, combined with its affordability and speed that's more than
adequate for high-precision mastering environments, has been a major reason
why many replicators aren't too anxious to switch to a new medium. In the
long-term, however, could DVD-R do for DVD replication become the mastering-source
standard that CD-R became for CD-ROM replication? Veterans of early CD-ROM
publishing recall that CD-R, like DVD-R, wasn't always ideally suited for
making masters. But as the format evolved, so did the replication community's
acceptance of it. Will the same thing happen to DVD--or has it begun happening
already? Now that 4.7GB DVD-R (version 2.0) media has been available for
some time--and further upgrades are imminent--has the replication industry
begun to embrace the optical format as a valid alternative to DLT?
According to the replicators, the answer is a unanimous and resounding "not
yet." While most of the major replicators have upgraded their equipment
to handle titles submitted on DVD-R and other alternative media, very few
titles-to-be are actually arriving on anything but DLT. "99% of material
that we receive is still submitted on DLT," says Bob Friedman, vice president
of technical operations at Crest National. "The industry itself is still
very much DLT-based." Even though replicators are seeing some titles that
are submitted on DVD-R, DLT tapes by far still outnumber the titles that
are sent in on DVD-R discs. "Although we are seing some 2.0 DVD-R media,
98% of what we receive is DLT," says Michael Strange, director of video
entertainment at Sony Disc Manufacturing (SDM).
Growing pains
DLT's monopoly as an input medium for mastering and replicating DVD titles
began because it was, quite simply, a format that worked. DLT supplied replicators
with a reliable format that had enough size and speed to guarantee the effective
transfer of the large files associated with DVD-Video. Because DLT has proved
itself to be a dependable media, DVD authors and replicators have almost
exclusively used the tape format.
While DVD replicators and authors have had time to become familiar with
the ins and outs of DLT, DVD-R in its current form (given the format's multiple
versions and intermittent states of flux) is comparably new. And as with
every new form of media, it has experienced a few growing pains. "We've
had problems in the past with DVD-R media, similar to the problems that
we had with CD in the beginning," says John Town, vice president of Research
and Development at Technicolor. "The mastering tools made for DVD-R are
beginning to get better, though." Replicators do note that the version 2.0
media has had less errors associated with it than version 1.0 media. DVD-R
is also beginning to receive full support from companies such as Doug Carson
Associates and Eclipse, makers of laser beam recording, mastering, and testing
software and hardware, which will allow replicators to have greater flexibility
when dealing with DVD-R.
The CSS Issue
Probably the biggest reason why most replicators choose DLT over DVD-R is
DVD-R's handling of Content Scrambling System (CSS) information--or lack
thereof. "The problem is that there aren't any drives--at least any that
are widely available--that can pull CSS keys off a DVD-R disc, let alone
write a CSS-encrypted DVD-R," says Town.
According to Pioneer's Andy Parsons, while it is impossible to write CSS
information to a DVD-R General use disc, DVD-R for Authoring discs do have
the ability to store CSS information. DVD-R General media ship with the
area where the CSS information is stored pre-blocked by the manufacturer.
While DVD-R Authoring discs are not blocked in this manner, the area is
unconditionally prewritten with null data when a first recording session
is performed on a disc by the only available DVD-R Authoring drive (Pioneer's
DVR-S201). Indeed, DVD-R's inability to handle CSS information almost single-handedly
rules out DVD-R's use as mastering media for DVD-Video in the studio entertainment
space where most DVD-Videos to date have fit to date.
Of course, few titles of non-Hollywood origin require CSS encryption. DVD-ROM
developers in particular may find that burning a title to DVD-R disc and
shipping it to the replicator may be more convenient than investing in DLT
devices and adding extra output steps to the process. "All of the material
that we've received on DVD-R has been for DVD-ROM," says John Town. As the
installed base of DVD-ROM drives steadily increases--along with corporate
and desktop use of the technology--one might guess, so would the number
of DVD-ROM titles being produced.
Size does matter
Another drawback of DVD-R as a source medium for replication is its size.
Although the capacity of DVD-R has improved, from 3.95GB to 4.7GB, many
DVD titles are now being replicated to DVD-9, which has a capacity of 8.5GB.
"I would estimate that between 70 and 75 percent of the DVDs we produce
are DVD-9," says Friedman. "The number of titles that are replicated to
DVD-9 has swelled," agrees Michael Strange, director of video entertainment
at Sony Disc Manufacturing (SDM). "You just can't use a 4.7GB DVD-R for
a DVD-9."
Consequently, many replicators remain skeptical about DVD-R's chances of
making inroads as a source material for DVD-Video replication. Nowehere
in the DVD-R roadmap appear to be provisions for adding a second recording
layer. This would seem to rule out DVD-R's ever overcoming this aspect of
its insufficiency as a mastering source. "DVD-R is limited in what it can
do (in terms of replication)," says Friedman. "Most authors would have a
hard time trying to fit a DVD-9 onto a 4.7GB disc."
While the dual-layer DVD-9 may be beyond the capacity of DVD-R, the discs'
4.7GB capacity makes it an attractive media for replicating DVD-5, as well
as the dual-sided DVD-10. "You certainly can use two DVD-Rs for the replication
of one DVD-10, but we haven't seen too much of this yet," says Strange.
"Although the ability to do DVD-5 and DVD-10 may be a plus for DVD-R, a
huge drawback is its inability to do DVD-9. "The big hangup with the current
DVD-R media is that it can't do DVD-9," agrees Friedman.
Good, not great
While DLT certainly is the media of choice for most replicators, it is not
without its share of limitations. Its speed, for one, may cause problems
when cutting a glass master straight from the tape. "Data has to come off
of the DLT tape fast enough to keep the buffer full," says Friedman. "If
the tape has to do retries, the buffer may abort cutting to the master."
As a solution to this problem, some replicators load everything from the
DLT tape to a large SCSI hard drive, before cutting the master. While this
may add to total replication time, copying to a hard disk allows some replicators
to have flexibility in which formats they accept. Technicolor, which loads
everything onto its network before cutting the glass master, sees an advantage
of moving everything to a neutral medium before cutting. "Loading everything
onto the network allows us to verify everything, bit for bit, from the input
media," says Town. "It also allows us to avoid DLT's speed issues when cutting
the glass master."
Still number one
Shortcomings with DVD-9 aside, a few replicators do see a use for DVD-R
in replication and mastering tasks. However, the appeal may be stronger
on the authoring side than the replication side. "I see market desire for
using DVD-R," says Strange. "We still prefer DLT, but that could change
very soon. The DVD-R could emerge as an easy-to-use format." Indeed, for
smaller DVD titles which don't use CSS encryption, as well as DVD-ROM, DVD-R
might prove to be beneficial. "As far as the media goes, DVD-R is getting
better, with less read errors," says Friedman. "And although the reliability
of DVD-R is increasing, we still receive the majority of our material on
DLT."
So what does the future hold for DVD-R's use in the replication arena? Most
replicators see DVD-R making some inroads, especially in the area of DVD-ROM
and smaller, independent DVD-Video titles. The consensus is that although
the use of DVD-R, as well as other high-capacity optical media such as DVD-RAM,
will increase, DLT is not going away anytime soon. http://www.emedialive.com/news/2001/01/news0101-01.html |
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