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Recordable & Rewritable Blu-ray Disc: How Far, How Fast?

As Blu-ray Disc’s (BD) entrance draws near, I’m increasingly asked about its writable formats. How long will it take to record a BD disc? How much will its writing speeds increase in the future? How quickly will it get there? And, frankly, is there a way for the industry to avoid past problems and intelligently ramp up to these speeds?


Recordable & Rewritable Blu-ray Disc: How Far, How Fast?

Hugh Bennett
EMedialive, September 20, 2005

As Blu-ray Disc’s (BD) entrance draws near, I’m increasingly asked about its writable formats. How long will it take to record a BD disc? How much will its writing speeds increase in the future? How quickly will it get there? And, frankly, is there a way for the industry to avoid past problems and intelligently ramp up to these speeds?

As a matter of background, BD discs will come in prerecorded (BD-ROM), recordable (BD-R) and rewritable (BD-RE) versions with both single (SL) and dual-layer (DL) types possible. Although several configurations will be officially supported, typical 8cm discs hold 7.791GB (SL) or 15.582GB (DL) and 12cm discs 25.025GB (SL) or 50.050GB (DL). Single-speed (1X CLV) BD writing takes place at 35.965Mbps (equivalent of 3.25X in DVD terms). The first wave of recorders, however, is expected to launch at 2X. At 2X, full 8cm discs will take on the order of 14.5 minutes (SL) and 29 minutes (DL) to write; the recording of full 12cm discs will clock in at 46.5 min (SL) and 93 min (DL).

Astonishingly, though BD has yet to make it to market, manufacturers already promote increases to 4X and then 6X speed. At this stage, anticipating anything further is only speculative, but it’s possible to make some informed predictions. Consider, that for a variety of reasons, including sound levels, vibration, as well as safety concerns, spinning an optical disc at 10,000RPM has long proven the realistic limit for half-height drives and 5,000RPM for slim-types. Since a 12cm BD disc rotates between 1957 to 810RPM (inner to outer diameter) at 1X speed, it looks to me as if 12X CAV (5X to 12X) will be the maximum potential ceiling for computer and 6X ZCLV or PCAV (2.5X to 6X) for portable BD units. If blank disc and component design can keep up, full 12cm BD-R (SL) discs may be eventually written in as little as 11 to 25 minutes respectively. Generally, rewritables and multi-layers are trickier to record at high speeds, so it’s possible that 5X or 6X may be the top end for BD-REs and DLs.

Relentless competitive and other market pressures assure that these recording speeds will escalate even more rapidly than the brief few years it took for writable DVD. It also looks to me as if manufacturers plan yet again to release every speed boost (4X, 6X, etc.) as soon as it becomes technologically possible. Each turn of the screw yields a brief opportunity for product differentiation and, hopefully, superior return. This will, however, come at a high cost as it did with writable CD and, especially, DVD—reduced product predictability and quality, a snarl of incompatible media types, quasi-supported performance levels, dissimilar writing speeds among physical formats, premature obsolescence, and overall complexity. The result, as always, will be confused consumers, suspicious professionals, beleaguered retailers, manufacturers, product developers and PC builders and intellectual property theft and counterfeiting, to name but a few.

Rather than unleashing a flurry of incremental advances of questionable value, a saner approach will be for the BD community to immediately establish a couple of meaningful targets and limit increases to these. Given my admittedly rough calculations, 5X or 6X and then 12X should be the focus of all writable BD development efforts. And if HD DVD also makes it to market, I challenge its architects to bite the bullet and do the same within its design boundaries.

Lamentably, as always, I’m pessimistic. Given the optical storage industry’s dismal track record I expect writable BD to end up just another free-for-all.

ABOUT THE AUTHOR
Hugh Bennett, editor-in-chief of Hugh’s News, is president of Forget Me Not Information Systems, a reseller, systems integrator and industry consultant based in London, Ontario, Canada. Hugh is author of The Authoritative Blu-ray Disc (BD) FAQ and The Authoritative HD DVD FAQ, available on Hugh’s News, as well as Understanding Recordable & Rewritable DVD and Understanding CD-R & CD-RW, published by the Optical Storage Technology Association (OSTA).

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