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Dual-Layer DVD and Beyond
(Sony DRX-800 Dual Layer DVD Burner, 9/2005)
by Douglas Dixon
See also Multi-Layer High-Def DVD Technology
Remember the arrival of CDs? What a big improvement on floppy discs, expanding storage from around 1 MB to 650+ MB! Then we moved on to DVD, bumping capacity up to 4.7 GB. While the 6X improvement from DVD was welcome, it was nothing like the previous 600X jump from floppies to CD -- although DVD provided the additional benefit of keeping compatibility with the previous generation of optical discs, so we now can have single drives that read and burn all flavors of CD and DVD.
So what's the next generation of removable storage? Actually, we're seeing both incremental improvements and a jump to the next technology -- We can get more storage from DVDs today with the availability of 8.5 GB dual-layer discs, and can see the impending arrival of blue-laser high-def DVDs offering 15 to 25 GB per layer. Them expanding beyond dual-layer to multi-layer HD discs, we can see 30 to 50 GB per disc and beyond, offering the promise of a 6X to 10X capacity improvement over the next couple of years.
If you're running out of room with "only" 4.7 GB on a DVD disc, relief is at hand with the availability of dual-layer recordable discs. Unfortunately, the DVD industry has terribly confused the picture, not only with two recordable formats like CD (write-once "R" and re-writable "RW), a smorgasbord of recording speeds (DVD from 4X to 16X and CD up to 48X), and the additional mess from two competing formats ("dash" and "plus"). A partial answer to this mess comes from the development of multi-format burners, that just support any format you throw at them.
Sony's latest multi-format burners, released in May 2005, are the Sony DRU-800A internal drive and the DRX-800UL external drive (around US$130 and $210, respectively, www.sony.com/dvdburners). The external DRX-800UL drive that I tested supports both Hi-Speed USB 2.0 and i.Link / IEEE 1394 interfaces, which makes it really easy to connect to recent laptops with USB 2.0 connections. It can be stacked horizontally, or mounted vertically if that works better in your space.
Sony describes this product as a "Double/Dual Layer & Dual Format DVD Burner," where the "Dual Format" part refers to supporting both competing formats for recordable discs: the original DVD Forum dash ("-") format (www.dvdforum.org), and the DVD+RW Alliance corresponding plus ("+") format (www.dvdrw.com). This means you don't have to worry about what kind of disc you have around, or can find at the store, you can just burn any available disc.
Then there's that "Double/Dual Layer" part of the product name -- Can't we even agree what to call counting to two? What this language means is that these drives support two-layer recording for both formats, the new DVD-R recording format which the DVD Forum's dash team calls "Dual Layer," and with the DVD+RW Alliance's corresponding plus format called "Double Layer." (There was an idea to talk about "double" sided discs, and "dual" layered discs, but now the best approach is just to call them by the shorthand "DL" -- and not worry exactly what the "D" stands for.)
Next, there's all those speeds -- these drives support 4X DVD±R DL recording, 16X DVD±R, 8X DVD+RW, 6X DVD-RW, 48X CD-R and 24X CD-RW. Just as CD recording speeds have increased dramatically, DVD speeds are growing as well. However, be aware that 1X CD is not the same as 1X DVD -- the 1X refers to the original speed to play through a disc in an hour -- so you play an Audio CD at 1X to listen to the entire album in about an hour, transferring 650 MB at 150 K Bytes/sec. But if you watch a one-hour DVD movie at 1X, that requires transferring 4.7 GB much faster at 1.3 MB/sec. These days, fast CDs are spinning at 48X, transferring data at 7 MB/sec., while DVDs are up to 16X, transferring 22 MB/sec.
But don't get greedy for more: these discs are spinning at rates up to 10,000 RPM, which is asking a lot of an inexpensive drive, even for an enclosed hard disk, much less an even less expensive optical disc where any imperfections at those kinds of speeds could cause the disc to fly apart. Sony actually sets the maximum CD speed to 40X on this product, and requires a manual override for each disk for a "Turbo Boost" to 48X, warning that a scratched or brittle disc may break at the higher speed.
Similarly, DVD media is pretty maxed out at 16X, and manufacturers like Verbatim are already there, with 16X write-once recordable DVD-R and DVD+R discs that can burn an entire disc in as little as 6 minutes (depending on the time to prepare the burn and finalize the disc). Just as with CD, rewritable DVD RW discs are recorded slower, with the drive supporting 8X write speed. (Officially, the current DVD-RW media is 6X, until 8X is certified.)
For two-layer recording, the drive supports 4X DVD±R DL recording (and 8X reading), and Verbatim released the required 4X DVD-R DL media in May 2005 for an estimated street price of $24.99 for a 3-pack in jewel cases (www.verbatim.com). Normal 4X DVD burning would take about 14 minutes to burn a single-layer disc, so burning two layers and 8.5 GB takes more like 28 minutes.
Verbatim DVD-R DL media
We can look forward to 6X and then 8X DL burning of write-once R discs starting to ramp up later this year, but 16X is significantly further away. Rewritable RW DL discs also are not a near-term prospect, so you'll have to make do burning 8.5 GB to a disc to use for backups and longer-form DVD-Video productions.
One more detail in burning DL discs is having the appropriate software that knows how to burn to both layers, and how to properly divide 8+ GB of data to insert a layer break between the two halves. Sony ships a slightly reduced version of the Nero 6 Ultra Edition DVD suite with its drives (www.nero.com), including the Nero Burning ROM and Nero Express CD/DVD mastering software for data, audio and CD/DVD writing, plus Nero VisionExpress 2 VCD/SVCD and DVD authoring software, and a broad collection of other tools and utilities. If you already have the Nero 6 Ultra Edition suite, you can download the free version 6.6 upgrade for full support.
Nero 6 runs on Windows 2000 & XP. Sony does not bundle Macintosh software, but the burner is compatible with Macintosh G4 / G5 systems running Roxio Toast version 6.06 or higher (www.roxio.com). Otherwise, check your DVD software to check that it is compliable with DL drives, both DVD+R DL and the new DVD-R DL.
The other compatibility issue with DL discs is that some older DVD players may not recognize the format -- DL recordable discs did not exist when the players were built. If you author DL DVD-Video productions, make sure to check playback on your target player device.
So DL is here now, but with only a 2X increase in capacity, which brings us to the promise of blue-laser discs and even more layers. Shifting from red to blue laser allows squeezing more information on a disc -- the wavelength shrinks from 650 to 405 nm, so the blue-laser beam spot size can be 1/5 that of current red-laser DVD. And, of course, smaller pits means more data on the surface of the disc. While this sounds great for data storage, the real driving force behind the development of blue-laser discs has been the desire to fit high-definition movies on disc. However, high-def requires around a 6X improvement in capacity (to support 1920x1080 video, in comparison to standard-definition 720x480).
Unfortunately, not satisfied with the confusion caused by the competing "dash" and "plus" recordable formats, the DVD industry has become embroiled in a full-fledged format war over blue-laser discs. In one camp is HD DVD, an incremental improvement championed by Toshiba and NEC, and officially accepted by the DVD Forum consortium (see www.hddvdprg.com). In the other camp is Blu-ray Disc (BD), a more aggressive step forward championed by Sony and Panasonic, with strong support from the consumer electronics and computer industries (see www.blu-raydisc.com).
With a more conservative design, HD DVD offers 15 GB of capacity per layer, or 30 GB for a DL disc. The Blu-ray camp is more interested in taking a larger leap to the next generation, and offers 25 GB of capacity per layer, or 50 GB for a DL disc. The HD DVD camp then responds that its format will be easier to manufacture, and therefore will be less expensive. But 50 vs. 30 GB per disc! -- That's 2/3 more storage for Blu-ray -- probably worth a price premium, even before prices decline with mass manufacturing.
The worst part of this format war is that it's not like dash vs. plus -- it's worse, more like VHS vs. Beta. With dash and plus, once you burned a disc, it was designed to be compatible with all DVD players -- the format only mattered when burning. With HD DVD and Blu-ray, the physical formats are different, so the discs will only play in a compatible player. This is not only a pain for consumers burning and sharing recordable discs, but also for the movie studios who want to release their content on a high-def format. Clearly, the uncertainty, and fear of choosing the "wrong" format, will slow the adoption of blue-laser DVD.
There's been talk recently of a grand reconciliation between the two formats. But this is not just a matter of changing specs on paper. Both camps are well along in the development of test disc manufacturing and replication lines with a broad array of partners -- they have produced millions of discs, and have published results showing they have the factory manufacturing processes under control, already close to the times and specs for current DVDs.
In addition, Sony already has been selling high-end Blu-ray set-top recorders in Japan, and is using Blu-ray for its ProData professional data disc line and the XDCAM professional disc camcorder line. And Sony has announced that the next PlayStation 3 (PS3) computer entertainment system will adopt the Blu-ray Disc ROM (BD-ROM) disc format.
Meanwhile, both camps are lining up Hollywood studios and broadcasters to support their formats. HD DVD is promising to ship players before the end of 2005, and studios have announced some 90 titles to start shipping in Q4. The Blu-ray camp is more interested in full-function devices that both play and record, and is finalizing the content protection technology before shipping products, targeting early 2006.
But remember that a key driver for blue-laser DVD was the need to support HD content, requiring a 6X increase in capacity. However, HD DVD is only 3X, and even Blu-ray is 5X the size of DVD, so something else is still needed besides raw capacity. The answer is to switch from the MPEG-2 compression used for DVD to newer formats -- both HD DVD and Blu-ray will still support MPEG-2, and also have adopted both MPEG-4 AVC (also known as H.264, www.mpegif.org) and Windows Media Video (being standardized as VC-1, www.microsoft.com/windows/windowsmedia). These next-generation formats compress significantly better than MPEG-2 (requiring only around 1/3 to even 1/5 the space), allowing blue-laser discs to hold full-length HD features, plus additional material.
But don't count out red-laser yet. The same improved compression opens the tantalizing possibility of storing more material, even HD, on discs much closer to plain old DVDs. This is the approach taken in China with the EVD (Enhanced Versatile Disk) format and in Taiwan with FVD (Forward Versatile Disc). These are intended to provide lower-cost alternatives to DVD and high-def DVD by working with red laser, adopting newer compression formats, and avoiding at least some of the licensing fees required for the standard formats.
See also Multi-Layer High-Def DVD Technology
Of course, once you've got a DL blue-laser disc holding 30 to 50 GB, why stop at just two layers? Why not three, or four, or even eight? Both the HD DVD and Blu-ray camps are busily at work developing multi-layer blue-laser discs, and hybrid / combo discs that combine both red-laser DVD and blue-laser layers.
In the HD DVD camp, Toshiba announced a dual-layer dual-format disc in December 2004, with both an upper 4.7 GB DVD layer and a lower 15 GB HD DVD layer. However, most Hollywood releases these days are on dual-layer DVD-9 discs, and HD features also could use more than just 15 GB, so just a single layer of each was not so exciting.
In May 2005, Toshiba announced the development of two more improvements. One is a triple-layer HD DVD disc, bumping the available capacity to 45 GB. The other is a double-sided disc, with a dual-layer DVD on one side (8.5 GB), and a dual-layer HD DVD on the other (30 GB). That's 38.5 GB total, which should allow studios to release full-length features in both formats on a single disc.
Meanwhile, in the Blu-ray camp, in December 2004 TDK announced a Blu-ray/ DVD combo ROM disc with three layers: an outside BD layer with 25 GB and two inner DVD layers (8.5 GB). That's 33.5 GB in a single disc, and on a single side -- leaving room for a label on the other side, and with no need to flip over the disc.
But why stop at three layers? In June 2005 TDK announced that it had developed a prototype 4-layer recordable Blu-ray Disc, with a 100 GB capacity and double the data rate of current BD (from 36 to 72 36 Mbits/sec.). TDK also is working on a 4-layer Blu-ray / DVD combo disc, with both 50 GB BD dual layer and 8.5 GB DVD dual layers.
And is four enough? Sony and the Blu-ray camp have also demonstrated 8-layer discs in a laboratory environment, for a whopping 200 GB capacity. And again, these expanded BD discs are all single-sided.
One of the significant technology challenges for the development of blue-laser discs is the tighter tolerances required for keeping an even narrower beam of light correctly positioned to read a ridiculously tiny pit of data on a rapidly-spinning plastic disc. Smudges of dirt and greasy fingerprints are bad enough on today's DVDs, but imagine the problems they could cause on high-def discs, especially when trying to punch a laser beam though the surface to read the disc, much less write the disc with precise pits of data.
One solution is to use a cartridge to protect the disc. This works well for the professional Blu-ray applications, but is totally unacceptable for a consumer product. Instead, this need has lead to the development of "hard coat" surfaces to protect discs so they can be handled by consumers (and their kids) without requiring excessive caution and care. As a bonus, these new surfaces are already becoming available for today's recordable DVDs, with products like Verbatim's VideoGard, TDK's DURABIS, and Imation's ForceField disc lines that promise up to 40X more scratch resistance and 20X more dust resistance than standard DVD media.
These surfaces have three benefits:
- They resist scratches and scuffs -- The surface can survive ordinary handling, so you no longer need to handle discs carefully by the edges, and even can casually stack discs or slide them on a table.
- They resist smudges and grime -- Like rain water on car wax, fingerprints "bead up" and are easy to wipe away. Combined with the scratch resistance, this means that you can clean the surface of discs to remove grime by just wiping with any cloth.
- They resist dust -- The surface also repels dust particles instead of having them bind with a static charge. This means you don't need a lint-free cloth to clean discs, and can be less careful about storing bare discs between uses.
And this is not just industry marketing speak -- This is real science, measured using standard test methodologies. Initially, the hard coat products have around a 25 - 30% price premium, and are targeted to consumers who want higher-quality media to protect their important memories on disc.
Sony - DRX-800UL DVD Burner
Nero - Nero 6 Ultra Edition
Roxio / Sonic - Toast
Verbatim - DVD Media
HD DVD Promotion Group
Blu-ray Disc (BD) Association
Microsoft - Windows Media Video (WMV)
MPEG Industry Forum - MPEG-4 AVC / H.264