QUESTIONS ABOUND ON TOSHIBA-NEC RECORDABLE DVD PROPOSAL
Key details were missing or murky in Toshiba-NEC joint announcement Thurs. that they had developed HDTV-quality playback-only and recordable DVD format based on blue laser and recorder deemed to be alternative to recordable Blu-Ray system with which it would be mutually incompatible. On same day, Toshiba and NEC said they had proposed as-yet-unnamed system to DVD Forum for consideration as standard. That’s in direct contrast to tack taken by Blu-Ray group, which has said it sees no need to involve DVD Forum as Blu-Ray is system that’s separate from DVD.
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It couldn’t be learned whether technical data submitted to DVD Forum on Toshiba-NEC system were more extensive than those released to news media. Joint news release described system as using 405-nanometer blue laser to play 15/30 GB prerecorded HD- DVD discs and to write to 20/40 GB blank discs. But partners didn’t reveal discs’ recording time capacity. Also not stated was whether system could record in standard definition as well as in HD. Blu-Ray system provides 2 hours of HD recording time, 13 hours in standard definition, which backers describe as “VHS” quality at 3.8 Mbps data transfer rate. Blu-Ray can store up to 27 GB on single-sided, single-layer disc, more than 50 GB on single-sided, dual-layer disc. Capacities cited for Toshiba-NEC system are for single-sided discs, both single- and dual-layer.
Toshiba-NEC announcement said system was backward-compatible for playback of current DVDs, but didn’t say how. For example, it was unclear whether this was accomplished with blue laser alone or whether red laser pickup and redundant electronics were needed. Sources speculated blue laser could be used to read today’s prerecorded DVD-Video, but expressed reservations about blue laser’s capabilities with dye-based blank discs used for home DVD recording.
Not addressed at all in Toshiba-NEC specs was video compression system being used. They simply said disc capacities were “achieved by employing a blue laser, and by utilizing the 2 companies’ new signal-processing and phase-change media recording technologies.” Toshiba in past has discussed using MPEG-4 compression with red laser for HD prerecorded-only DVD system. Blu-Ray system uses MPEG-2 compression, same as today’s DVD and HDTV, and has 36 Mbps data transfer rate. Toshiba-NEC proposal uses same rate and what companies called “PRML” signal processing. PRML (for “Partial Response Maximum Likelihood") technology has applications in hard disc drives with magnetoresistive heads. It’s method of sampling waveforms of data on disc to derive cleaner signal with fewer errors and at faster data transfer rate. It couldn’t be learned how or to what purpose Toshiba-NEC system applied PRML to optical discs and laser pickups. Answers to that and other queries weren’t available from Toshiba and NEC Thurs. owing to time difference with Japan.
Despite missing specs for Toshiba-NEC system, differences are obvious between it and Blu-Ray proposed by Hitachi, LG, Matsushita, Philips, Pioneer, Samsung, Sharp, Sony, Thomson. Each system uses blue laser with 405-nanometer wavelength, but numerical aperture of laser’s lens is 0.85 for Toshiba-NEC compared with 0.65 for Blu-Ray. Possibly accounting for difference is different makeup of discs. Toshiba-NEC disc is made by back-to-back bonding of 2 discs, each 0.6 mm thick, just as with today’s DVDs. Blu-Ray disc also has 1.2 mm total thickness, but has 1.1 mm substrate covered by 0.1 mm “optical transmittance protection layer.” 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.
Similar construction 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 contend their disc doesn’t need protective caddy or cartridge for insertion into hardware and thereby makes it possible to manufacturer slim drives, including for portables. Original specs released by Blu-Ray Founders called for protective cartridge that’s 7 mm thick, and 9 mm to 11 mm larger than disc’s 120 mm diameter. However, we have been told in past that actual need for caddy remains under discussion among Blu-Ray developers.
Although DVD Forum has 2 subgroups to study different blue- laser recording technologies based on discs with 0.6mm and 0.1mm cover thickness, Blu-Ray’s proponents haven’t proposed system to DVD Forum and have said they didn’t feel need to, saying Blu-Ray was format completely separate from DVD and hence DVD appeared nowhere as part of Blu-Ray logo. Still, format might have future as DVD Forum standard.
Despite Toshiba-NEC proposal for rival system, Toshiba spokeswoman left open possibility that Blu-Ray system could be implemented as HD recording format further in future as storage needs increased. Toshiba in past has said it’s officially “neutral” on Blu-Ray, and although it won’t join Blu-Ray consortium it continues to pursue development of that format. Spokesman earlier this year said Toshiba believed development of next-generation optical disc recorders for HDTV was “still at the initial stage and we expect multiple technologies to come out in coming months or years” and that company hoped all technology developers would submit their proposals to DVD Forum “so we can derive the best format in the future.”