Paris — Unification of the HD DVD and Blu-ray Disc optical formats is being discussed in earnest, sources on both sides have confirmed. With a compromise perhaps only months away, the rival camps must now confront the difficulty of reconciling schemes that have little in common beyond their basis in blue lasers.

The negotiations remain fluid, but at least two proposals are on the table for merging aspects of the two high-definition formats, sources said last week at the National Association of Broadcasters convention in Las Vegas (see www.eet.com/news/latest/showArticle.jhtml?articleID=16090147 5).

One is a hybrid solution that would support Blu-ray for recording and HD DVD for ROM disks. The other seeks commonality on the higher-level protocol and the disks' interactive layers, if not on the full physical format.

The Blu-ray group had held marathon meetings at Disney studios in the week preceding the NAB convention, and the DVD Forum is meeting at Warner Bros. this week. Sources close to the forums noted that the Blu-ray group has been evolving its own format as it explores convergence with HD DVD.

Clearly, the two sides hope to avoid a format war. New Sony Corp. president Ryoji Chubachi has stated that bringing two formats to market would be counterproductive, and others echoed his comments at a recent meeting in Tokyo.

"For healthy industry development, it is of course desirable to avoid a useless fight," said Shinichi Tanaka, the director of the Storage Media System Development Center at Matsush*ta.

And not a day does by, said Hiroharu Satoh, general manager of Toshiba's HD DVD Promotion Division, that he does not think about "a way to come to an agreement on a single format."

The technical differences between the formats are not trivial. Both use a blue laser and support similar video compression formats. They may implement the same copy protection mechanism, sources speculated, although Blu-ray has not announced its choice.

But the Blu-ray framers, shooting for higher storage capacity and future expandability, adopted a disk structure in which the recording layer sits on a 1.1-mm thick substrate and a 0.1-mm cover layer protects the recording surface. To focus on the recording layer, Blu-ray uses an objective lens with a numerical aperture of 0.85. That establishes it as a new format, with little continuity from current DVDs.

For HD DVD, by contrast, such continuity is a selling point. The disk is similar in structure to DVDs, with two 0.6-mm-thick platters bonded together. The lens aperture is 0.65, slightly higher than DVD's 0.6. The similarities make it easier to develop a single lens-pickup head that can drive all CDs, DVDs and HD DVDs; it also facilitates disk replication. Disk replication company Memory-Tech Corp., an HD DVD supporter, has been able to demonstrate the quick conversion of disk-processing lines from DVD to HD DVD.

Comeback proposal
The idea of partitioning usage, with HD DVD applied for ROM disks and Blu-ray for recording, was tabled by the DVD Forum before Blu-ray's proponents broke away from the forum to pursue their own spec. But the HD DVD camp has resubmitted that proposal, sources said at NAB.

A hybrid solution might be a good fit for the studios, which have diverging interests for the next-generation spec, sources said. Warner Bros. is reportedly seeking the lowest-cost medium, whereas capacity is said to be the priority for The Walt Disney Co.

But the hybrid proposal poses unanswered questions, such as how to design the laser pickup to accommodate lenses of different numerical apertures, and whether a device that supports two lenses can be made compact enough for mobile gear.

The other proposal seeks consensus on unifying the logical layer of next-generation disks, if not the physical disks themselves. That approach is attractive to studios because it would allow them to author a title and compile it for either platform with a minimum of effort.

It's a scenario that seems destined to confuse consumers and double sellers inventories. From an electronics industry standpoint, however, a unified logical layer for next-generation disks is a pragmatic approach that would lessen the software and hardware development burden. Player manufacturers could depend on a common set of application programming interfaces to handle interactivity. The approach, while less than perfect, could speed next-generation DVDs to market.

The gorillas
As the two sides negotiate to prevent a format war, two 800-pound gorillas loom over the proceedings.

One is the question of intellectual-property rights. "I do not see how you would compromise here to take parts of one technology and combine it with technology of the others," said Stuart Lipoff, partner at IP Action Partners (Newton, Mass.). In his view, successful negotiations to unify formats don't happen without all parties first "agreeing to pool all the patents on a royalty-free basis. . . . Toshiba and NEC throw into the pot their HD DVD patents, and Sony, Hitachi, LG, Panasonic, Pioneer, Philips, Samsung, Sharp and Thomson throw in their Blu-ray patents."

Second, Lipoff said, the players must "all meet together and agree on a product introduction road map that starts with HD DVD and has a future migration to Blu-ray." That second step is needed, he said, because "HD DVD has the advantage that existing manufacturing facilities can be used, so it can support a wider range of HD titles faster. But [its storage] capacity is lower than Blu-ray's, and there is concern about delivering the quality consumers will demand for long HD movies."

That will dictate a transition to Blu-ray over time, Lipoff said, even though that format will require manufacturing changes that will be "expensive to do."

During the first DVD format battle, 10 years ago, negotiations between the camps didn't get off the ground until Sony and Philips, in a surprise move, abandoned their proposed format but succeeded in forging an understanding that their IP would be included in the converged DVD format along with that of the competing camp, comprising Toshiba, Time Warner, Matsush*ta, Pioneer, Thomson and others.

Although the DVD Forum failed to create a one-stop patent pool for all intellectual property related to DVD, the spirit of IP sharing created the impetus for development of a unified format.

The other behemoth looming over the discussions is Microsoft Corp. Sources confirmed that the Blu-ray camp is developing its interactive software on the Java-based Multimedia Home Platform/Globally Executable Multimedia (MHP/GEM) platform. The HD DVD group has based all of its advanced software on a derivative of Microsoft's MSTV.

"On the software front, it is hard to imagine picking anything other than MHP," said IP Action's Lipoff. He called MHP the clear winner in the TV world, noting that it's widely used in Europe and is the underlying platform in the United States for the OpenCable Application Platform, developed by CableLabs, and the Advanced Common Application Platform for future interactive digital-TV broadcast services.

"For MHP, you already have development tools, experience and an installed base that will grow regardless of any DVD decision," Lipoff said. "I cannot imagine picking another software platform."

But another industry source, who spoke on the condition of anonymity, said he "can't imagine Microsoft giving up on interactive HD DVD. It's their heart and soul."

Both the Blu-ray and HD DVD disk formats can stand on their own, without using the advanced content APIs. But reportedly the studios have made it clear that the next-generation DVD format has to be more than just a movie player; advanced interactive and Internet capabilities will be requisite.

— Additional reporting by Rick Merritt