With blue-laser technology and double capacity DVD+Rs on the horizon, your DVD drive may soon be obsolete. Again.

Just when you think it's safe to go out and purchase a DVD burner, new technology shows up - and in this case, there's three different kinds. The most innocuous new twist is 12x recordable - a speed jump that will save a bit of time, but otherwise won't make much difference.

More earth shattering is the forthcoming dual-layer, double-capacity DVD+R, as well as a more distant product, based on blue laser technology, called high-def DVD. Blue laser promises huge capacity and faster speeds, but, as is usual with DVD, a war is brewing over the high-def format.

Double duty

Dual-layer recordable DVD drives and media (also known as double-layer in the DVD+R format) possess roughly twice the capacity of current 4.7GB media and can hold an entire high-bit-rate, 8.5GB DVD-9 commercial movie. For consumers, that means comfortably fitting 3 hours or more of high-quality video on one disc. However, informal tests suggest that dual-layer discs may be incompatible with at least some current players and burners.

But several caveats are in order. A relatively minor one is that dual-layer DVD+R writing proceeds at only 2.4x, so it requires about 45 minutes to write a full disc. When using DL DVD+R, you must write a full disc to obtain the proper reflectivity on both layers.

More importantly, dual-layer discs will reach store shelves slowly - and will be temporarily expensive, says Verbatim spokesman Andy Marken. As more suppliers emerge, prices will probably drop drastically, but single-layer media will continue to be cheaper for the foreseeable future.

The most serious problem, however, is incompatibility with existing players and drives. State-of-the-art DVD burners from Plextor (the PX-712A and PX-708A) and Memorex Products (the True 8x) wouldn't recognize video that we burned onto a preproduction DL disc, and only four of the twelve DVD players that we tried to use would play it. Firmware upgrades should fix the burner problem on new models, and Marken says that the goal for production-level media is 90 per cent compatibility.

Benq, Lite-On Technology, Memorex, and Pioneer each plan to release a DL drive in the US within the next couple of months. These drives will support dual-layer for DVD+R. In addition, some existing drives may add DL write support via firmware upgrades. Consult your drive's manufacturer to be sure. The competing write-once format, DVD-R, should go dual-layer by the end of June, when the DVD Forum is expected to ratify the new specification.

Blue language

Despite receiving considerable press attention, blue-laser DVD is hardly poised to take over from today's DVD technology. Even the most optimistic analysts don't expect blue laser to have more than a minor market impact for at least five years. But the battle is on over whose format will win the hearts and minds of Hollywood - not to mention a boatload of future royalties.

Of numerous combatants, just two formats appear headed for the big showdown - the DVD Forum's HD-DVD, created by Toshiba and NEC, and Sony's Blu-ray, which is supported by practically everyone else. China is following a different path with EVD (Enhanced Versatile Disc), yet another standard, but the impact of EVD in other countries is uncertain.

In comparison to the red-light lasers used in current CD and DVD products, blue-light lasers possess a shorter wavelength - 405 nanometers versus red laser's 650 nanometers. That translates into speedier pulses and smaller marks positioned closer together, yielding greater capacity and faster speeds. One beneficiary will be HDTV, which offers up to 1,125 lines of resolution and up to 19.4-Mbps transfer rates. Two hours of material transmitted at this speed requires just over 19GB of storage, far more than single- or dual-layer discs now offer.

The DVD Forum, NEC, and Toshiba claim that HD-DVD, which increases the capacity of DVD from 4.7GB to 15GB per layer, is easier to implement and could be brought to market more quickly and less expensively because it doesn't necessitate a complete retooling of existing assembly lines. In fact, NEC has already announced production of a dual red/blue laser read/write head (but no accompanying drive) that is backwards-compatible.

Nevertheless, since single-layer HD-DVD capacity falls short of the minimum requirement for handling 17.5GB HDTV - as does the 15GB EVD standard - the DVD Forum is accommodating compression schemes besides today's tried-&-tested MPEG-2, The MPEG-4-compliant H.264, and Microsoft's Windows Media 9. Both permit compression ratios higher than MPEG-2 at similar quality, but would require the DVD player manufacturers to pay additional royalties.

Sony and others argue that a clean break with older technology will result in greater capacity; Blu-ray offers from 23.3GB to 27GB per layer, easily exceeding HDTV requirements. Not surprisingly, Blu-ray is sticking with MPEG-2, although its creators haven't ruled out using other codecs.

Neither the HD-DVD nor the Blu-ray spec is graven in stone yet. To muddy the waters further, MPEG-4 playback is already appearing on some current DVD players such as NextWave Telecom's TW-3108 and Technosonic's MP-101. If adopted by other players and recorders, MPEG-4 may become a de facto specification.

The high-definition DVD fight is a minor story for now. The difference in quality between high-res DVD and current DVD is too small to give users a reason to upgrade until HD content becomes more widely available. Few people own TVs capable of showing off the higher resolution, and the new format's copy protection system will be far tougher than the weak one in current DVDs.

That said, the first blue-laser product is already on sale in the US - Sony's 23GB-per-layer Professional Disc for Data. At $2,996 (around £1,600) for an internal SCSI-3 drive and $3,300 (around £1,800) for an external USB 2.0/SCSI-3 version, it's a business backup option only, and the $45 discs it writes are not compatible with other types of drives.

12x standard DVD

Finally, though it's an incremental improvement, the first wave of 12x recordable drives is impressive. Plextor's £110 plus VAT) PX-712A burns discs at 12x and doesn't even need yet-to-be-released 12x DVD+R media to manage the trick It wrote a full movie in just over six minutes (at 12x) using Taiyo Yuden 8x DVD+R discs. There is a list of 12x-writable 8x media on Plextor's Web site. The PX-712A burns DVD-R discs at 8x, DVD±RW at 4x, CD-R at 48x, and CD-RW at 24x, too.

The dual-layer drives from Benq, Lite-On, Memorex, and Pioneer will boast 16x DVD±R speeds as well - but don't expect media for them to ship until some time this autumn.

Though there are clouds of confusion on DVD's horizon, your choice for the moment is fairly clear. The 12x drives will save you time and won't bust your budget. Sadly, the compatibility of dual-layer discs with current hardware is suspect, and the high initial price of discs means you may want to avoid the technology for the immediate future.