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Multi-Layer High-Def DVD Technology (9/2005)
    (Blu-ray Disc and HD DVD)

    by Douglas Dixon

High-Def DVD and Dual Layers
Hybrid Discs
Even More Layers
More Storage
References

How much capacity is enough? The move from floppy discs to CD was a huge jump -- a 600X improvement (from around 1 to 650 MB). While not as larger a jump, the 6X improvement from CD to DVD (to 4.7 GB), had the benefit of maintaining form factor compatibility with the previous generation. That same compatibility choice has been made in moving to the next generation of high-definition blue-laser DVD, which promises an even smaller step to another 3X to 5X capacity improvement (15 to 25 GB per layer, for HD DVD and Blu-ray Disc).

But is 15 to 25 GB really enough for high-definition movies? Well, moving from standard-definition to high-def requires a 6X increase in capacity (from 720 x 470 SD up to 1920 x 1080 HD). But these new formats are not just about raw capacity; they also will using more advanced MPEG-4 or Windows Media Video compression to reduce the video size, so it looks like the additional 3X to 5X improvement in raw capacity should be enough.

However, many of today's movies are delivered on 8.5 GB dual-layer DVD-9 discs, and often include lots of bonus materials and data, so there's still a need for additional space. As a result, both these format are coming to the market supporting dual-layer formats, providing 30 to 50 GB per disc. But why stop at two layers? Echoing hybrid formats like SACD and Dual Disc, both formats are promising dual-format discs that provide both red-layer DVD and blue-laser high-def DVD content, with the possibilities of multiple layers of each. And both are discussing more layers of HD content -- 2 to 3 to 4 to maybe 8 -- promising 45 up to 100 to 200 GB per disc!

The possibilities for multi-layer high-def DVD discs were discussed at the Next Generation DVD Summit, sponsored by the DVD Association (DVDA, www.dvda.org) coordination with the National Institute of Standards and Technology (NIST, www.nist.gov) in Gaithersburg, Maryland in June 2005 (www.dvda.org/html/nist-conference.php).

The speakers included Mark Knox, technical advisor to the HD DVD Promotion Group (www.hddvdprg.com), and Tony Jasionowski, senior group manager at Panasonic and Blu-Ray Disc Alliance spokesman (www.blu-raydisc.com).

High-Def DVD and Dual Layers

Both blue-laser formats have defined base formats in both single-layer and dual-layer versions.

The HD DVD format actually starts with today's dual-layer red-layer DVD 9 format, but with containing data stored in HD DVD format and the high-def video compressed using the approved codecs, H.264 (MPEG-4, www.mpegif.org) or VC1 (Microsoft Windows Media 9, www.microsoft.com/windows/windowsmedia).

Says Knox, "Since the physical format is the same as today's DVD 9, this will be the least expensive option to provide HD content. The capacity of 8.5 GB provides up to two hours of HD content if you use as the codecs."

The base HD DVD disc then is the HD DVD 15, with a single 15 GB layer (or some four hours of HD content). The dual-layer HD DVD 30 format then provides 30 GB (eight hours). The specifications for both these formats have been approved by the DVD Forum, and they will be available later this year. The cost for single-layer discs, says Knox, is "a few pennies more than today's single-layer DVD," while the dual-layer format is "about 10 to 15 percent more than a DVD 9." Both formats can be produced on the same production equipment as standard DVD. Millions of the single-layer and a half-million dual-layer HD DVD discs have been manufactured for testing, and have been used for demonstrations since January.

   

        Multi-Layer HD DVD-ROM

Similarly, the Blu-ray Disc (BD) format includes both single-layer (25 GB) and dual-layer (50 GB) formats for ROM and recordable discs. 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.

   

        BD-ROM Dual / BD-ROM Quad

To support Blu-ray manufacturing, Panasonic opened a pilot production line for Blu-ray Disc (BD-ROM) replication within its Torrance, C.A. disc manufacturing facility. According to Jasionowski, the plant has successfully started pilot production of 25 GB single layer spin-coated Blu-ray discs in June 2005, and Panasonic plans to spin-coat 50 GB dual layer BD-ROM discs as well.

In May 2005, the Blu-ray Disc Association reported that Singulus has developed replication systems that will target cycle times towards three seconds, with yields expected to exceed 90 percent for mass production. Sony has developed a Phase Transition Mastering (PTM) process that reduces the eleven steps currently used in DVD mastering to five for BD-ROM, requires as little as one-fifth of the space required for DVD mastering, and permits the equipment to be configured to allow mastering of both BD-ROM and DVD-ROM on a single system. Technicolor is establishing a complete pilot BD disc manufacturing process by July 2005, and Cinram has a pilot replication line that that produced demo discs for CES 2005 and is awaiting the delivery of commercial lines.

Hybrid Discs

Multi-sided and multi-layer discs also offer the possibility of offering dual-format or "twin format" discs, hybrid formats that combine both current standard-definition DVD and high-def DVD formats on the same disc. "Having this disc means studios can release movies on one format," says Knox, "that can hold both SD and HD content. The disc can be read by all of today's DVD players, so they can sell the discs to many consumers even if the installed base of HD DVD players is relatively modest. This also means consumers can use the disc on the big system in the living room as HD, or in the bedroom, on a laptop PC or in a car DVD player with the standard side."

Two such formats have been announced for HD DVD. The first is a single-sided, dual-layer hybrid ROM disc with one layer of each format. Announced in December 2004 by Memory-Tech and Toshiba, the disc contains both an upper DVD 5 layer (4.7 GB) and a lower HD DVD 15 layer (15 GB) . "This has been approved by the DVD Forum," says Knox, "but since most of today's DVDs are DVD 9, the studios were not so excited about it."

The second hybrid disc is a double-sided, dual-layer hybrid ROM disc, with one side containing dual-layer HD DVD 30 (30 GB), bonded to the second DVD 9 side (8.5 GB). It was announced by Toshiba in May 2005 at Media-Tech, and the draft specification was approved by the DVD Forum in June.

   

        Double-Sized HD DVD-ROM / DVD-ROM Hybrid Disc

Memory-Tech has stated that these formats can be produced on existing manufacturing lines, which can manufacture both HD DVD and DVD discs. Manufacturing costs for the single-sided dual-layer discs will be comparable with that of single-sided dual-layer DVD-ROM or HD DVD-ROM discs, and the cost for the double-sided format, says Knox, "is only a little more than today's DVD 18."

The Blu-ray camp also has been pursuing increase capacity with multi-layer and hybrid disc formats. While the HD DVD announcements have focused on ROM formats for replicated discs, Blu-ray has been exploring increasing capacity for recordable formats. The announced Blu-ray formats also are all single-sided, even with hybrid DVD-9 layers, leaving room for a label on the other side and simplifying consumer usage.

In December 2004, JVC announced a triple-layer combo Blu-ray / DVD ROM format combining an outside Blu-ray disc (BD) layer (25 GB) and an inner dual-layer DVD 9 (8.5 GB), for a total capacity of 33.5 GB.

   
        BD-ROM (25GB) + DVD dual (8.5GB)

The format uses a high-performance reflective film that reflects the blue laser used for Blu-ray, but is transparent to the red laser used for conventional DVD players. By using double-faced substrate molding with a BD layer on one side and one of the DVD layers on the other side, JVC reports it is possible to fabricate Blu-ray / DVD combo ROM discs with approximately the same efficiency as conventional Blu-ray ROMs.

In addition, JVC reported that it was working on a four-layer combo ROM disc combining dual layers of both Blu-ray (50 GB) and DVD (8.5 GB), for a total capacity of 58.5 GB storage.

Even More Layers

Or for the most capacity, just pile on more high-capacity layers. In May 2005, Toshiba announced a triple-layer HD DVD disc at Media-Tech. The HD DVD 45 has a capacity of 45 GB (12 hours). The draft specification for the format has been submitted to the DVD Forum, and should be approved "later this year," says Knox.

Knox reports that triple-layer demo material should be available in the summer, and that existing players can read the format, requiring only a firmware change. The discs could be available in 2005, he says, "although the very beginning of 2006 is more likely for volume production."

As described by Toshiba, the triple-layer discs are produced by back-to-back bonding of a 0.6mm-thick dual-layer disc and a single-layer 0.6mm disc. The single-layer disc is produced first, using the same process as HD DVD-ROM. Next, the second layer is formed on the first layer using a one-time polycarbonate stamper, the same process used for the double-sided dual-layer DVD-18 disc. Finally, the single-layer 0.6mm disc is bonded to the dual-layer disc, using standard technology.

"The manufacturing process is similar to today's DVD 14," says Knox, "but needs a little more precision since the bonding layer is in the optical path. There are four additional process steps compared to DVD 9, so this is the most expensive option, about 50% - 60% more than DVD 9. Frankly a lot of studios do not see the advantage of 45 GB capacity, as very few films need that much space. They also believe multiple discs are better in convincing consumers to spend the money they need to get for multiple movies or many TV series episodes.

Meanwhile, for Blu-ray, in June 2005, TDK announced the development of a prototype four-layer single-sided recordable Blu-ray Disc with 100 GB capacity, capable of storing 9 hours of HD video compressed at 24 Mbps. The disc also can record at a data rate of 72 Mbps, double the 36Mbps rate of current Blue-ray.

Sony and the Blu-ray camp also have demonstrated 8-layer discs in a laboratory environment, for a whopping 200 GB capacity on a single side.

More Storage

This all sounds wonderful, but is it really possible to pile on layers? Andy Parsons, senior vice president of product development for Pioneer USA, offers his perspective. On the one hand, the Blu-ray design closer to the surface has advantages for multiple layer discs: "When you talk about a .1 mm cover layer," he says, "it is much easier to produce more layers simply because you are not trying to focus the beam through such a thick layer of plastic material."

On the other hand, developing new formats requires both new engineering and cost-efficient manufacturing. "Eight layers is feasible," says Parsons, "but is it practical? We really don't know yet, because the manufacturing process will be different than dual layer, and is that going to be cost-effective?" Of course, he adds, "When DVD first shipped, everybody has said that dual layer was impractical, nobody was going to be able to do it, it was going to be too expensive. But it happened, and the price to make dual layer now is close to the price for single layer in quantities."

The other issue is backward compatibility. "You need to ask whether existing players will be guaranteed to play multiple layer discs," says Parsons. "It's not just the disk; it's not going to be as trivial as a firmware update, the tolerances are just so tight." In addition, new formats will not be successful if they come late to a market that already has a huge installed base. "If we can get them to market fairly quickly, even after the products are introduced," he says, "then they can be viable."

So here we go again -- yet another DVD format war, this time over blue-laser formats, again threatening to confuse consumers and slow the development of a new market. And yet the competition that this battle has fostered seems to be paying huge dividends in the rapid development of improved technology, including hard coat surfaces to protect discs and these multi-multi-layer disc formats -- and offering spin-off improvements for red-laser discs as well. By the time this all shakes out, the original capacity bump promised from moving to blue-laser DVD may well have been swamped by the bonus of extra layers.

References

Next Generation DVD Summit, June 2005
    www.dvda.org/html/nist-conference.php

DVD Association (DVDA)
    www.dvda.org

National Institute of Standards and Technology (NIST)
    www.nist.gov

HD DVD Promotion Group
    www.hddvdprg.com

Blu-ray Disc (BD) Association
    www.blu-raydisc.com

MPEG Industry Forum - MPEG-4 AVC / H.264
    www.mpegif.org

Microsoft - Windows Media Video (WMV)
    www.microsoft.com/windows/windowsmedia