DVD FORUM CLEARS AIR ON FUTURE HD DISC FORMATS

Group’s announcement contradicted statements by Toshiba and NEC to media, including us. Although comment wasn’t available from DVD Forum or AOD partners for Nov. 8 report, Toshiba spokesman following Mon. replied to our query, saying Toshiba-NEC “jointly proposed format was officially approved” by DVD Forum and that companies would begin finalizing format specifications. Earlier, Nikkei reported that NEC had said it would release AOD drive for PCs and PC with built-in AOD drive next year, and that Toshiba said it planned to market AOD home recorder in 2004.

DVD Forum’s statement reports status of its “consideration” of “optical disc formats utilizing blue laser diodes.” “In June 2002, the Steering Committee of the DVD Forum formed two Subgroups of the Forum’s standing Working Group 11 ’to study and promote the best technical approach based on’ 0.6 mm and 0.1 mm technologies respectively for blue laser optical disc applications,” statement said, alluding to 0.6 mm surface coating for AOD and 0.1 mm “optical transmittance protection layer” used by rival Blu-ray format. “At the same time, the Steering Committee also formed a Subcommittee to work with the Blu-ray Disc Founders toward reaching an agreement to work together on a common format. The first of the two Subgroups was formed in June, and is now studying 0.6 mm technology. To date, no 0.1 mm technology has been proposed to the DVD Forum. The DVD Forum has so far made no decision to adopt or reject any proposed format (either 0.1 mm or 0.6 mm) for blue laser optical disc applications.”

Statement’s reference to lack of “0.1 mm technology” proposal reflects fact that Blu-ray Disc group of Hitachi, LG, Matsushita, Philips, Pioneer, Samsung, Sharp, Sony and Thomson has long said format is different from DVD, so it doesn’t need to make proposal to DVD Forum for consideration as standard or right to use DVD logo. Status of “subcommittee” to work with Blu-ray on common format wasn’t addressed.

Technical differences abound between AOD and Blu-ray. Blu- ray disc holds up to 27 GB of data on one side, while AOD holds up to 20 GB. Although Blu-ray offers higher capacity, NEC and Toshiba contend AOD discs can be manufactured easily on existing DVD production lines. Blu-ray camp has contended its software is no more difficult or expensive to make.

When announced in late Aug. by NEC and Toshiba (CED Aug 30 p1), partners described as-yet-unnamed system that would use 405- nanometer blue laser to play 15/30 GB prerecorded HD-DVD discs and to record 20/40 GB blank discs. Capacities cited for Toshiba-NEC system were for single-sided discs, both single- and dual-layer. Partners said system would be backward-compatible to play current DVD-Video discs, but they were silent on other key details. Toshiba spokeswoman told us it would have 2-3 hours’ recording time for HDTV-quality signal on single-sided, single- layer 20 GB disc. Blu-ray provides 2 hours of HD recording time on single-sided, single-layer 27 GB disc, and 50 GB single-sided, dual-layer disc is planned.

Like Blu-ray, AOD format can record 13 hours or more of standard definition programming. Toshiba spokeswoman said HD recording could be expanded to 4 hours by using “more advanced compression technology.” Actual compression system for Toshiba- NEC format hadn’t been decided at time and still hasn’t been revealed, but would be either MPEG-2 or MPEG-4, spokeswoman told us.

Blu-ray format uses MPEG-2, same compression as for DTV and current DVD-Video. Latter is read with red laser and will be playable in Toshiba-NEC system, which will use single pickup that combines red laser for reading DVD-Video and blue laser for reading and writing HD-DVD. It’s not known yet whether system also will incorporate infrared laser for reading CD formats. Although sources said it technically was possible to use blue laser to read prerecorded DVD-Video disc, it wasn’t feasible for playback of dye-based blank discs used for home DVD recording. Among other reasons, dyes used for DVD blanks are optimized for reflectivity of red laser, they said. Although DVD-Video isn’t part of Blu-ray format, proponents said market demand would likely force inclusion of DVD Forum’s DVD-Video.

Prerecorded and blank AOD media for Toshiba-NEC proposal are based on current DVD-Video standard, which uses 1.2 mm-thick disc made by back-to-back bonding of 2 discs, each 0.6 mm thick. System’s 405 nanometer blue laser, used for reading and writing HD discs, has lens with numerical aperture of 0.65 -- close to that of 0.60 used for DVD-Video. Data transfer rate for HD video is 36 Mbps. Data transfer rate is same for Blu-ray, but that system uses different disc structure that has 0.1 mm “optical transmittance protection layer” above data layer on 1.1 mm substrate. Blu-ray data is played and recorded by 405 nanometer laser with 0.85 numerical aperture lens. Among other differences, Toshiba-NEC system uses land-and-groove track structure like DVD-RAM, while Blu-ray records only in grooves like DVD-R/RW and DVD+R/RW.

Disc construction similar to today’s DVD is key argument made by Toshiba and NEC for new system. Besides permitting playback compatibility with current prerecorded discs, they contend that retaining dual 0.6 mm bonded layers will enable DVD replicators and blank media makers to continue to protect their investments in current equipment. Partners also say their disc doesn’t need protective caddy or cartridge for insertion into hardware, which makes it possible to manufacture slim drives, including for portables. Original specs released by Blu-ray Founders called for protective cartridge that would be 7 mm thick and 9-11 mm larger than disc’s 120 mm diameter. However, we have been told that goal of Blu-ray developers is to eliminate need for caddy with blank discs; prerecorded Blu-ray discs don’t need caddy.