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Streaming Media
DVD-R versus DLT for DVD Replication
Posted Feb 1, 2001 Print Version     Page 1of 1
  

February 2001|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—have been major reasons why many replicators aren't too anxious to switch to a new medium. In the long-term, however, could DVD-R become the mastering-source standard for DVD replication 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. "Ninety-nine percent 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 seeing 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.

'de 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 ships 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.

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 that 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% 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. Nowhere 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 disc's 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 hang-up 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 the 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.

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