Next-generation DVD

By the late-1990s the blue laser represented the best chance that optical storage technology had for achieving a significant increase in capacity over the coming decade. The laser is critical to development because the wavelength of the drive's laser light limits the size of the pit that can be read from the disc, and for much of the 1990s efforts were being made to perfect the blue laser, in a form which could be used inside an optical disc layer. They have a smaller wavelength, so the narrower beam can read smaller dots.

In the event, blue lasers proved to be a difficult nut to crack. By the late 1990s they were used for making the masters for DVD discs. However, this process used hugely expensive special laser-beam recorders the size of a wardrobe and needing a super-clean, vibration-free environment in which to work properly.

The challenge was to make the blue laser in a form that can fit into a PC-ROM drive and be affordable. The amount of power the laser needs to produce is a lot for a device hardly bigger than a match-head. Getting the laser to fire out of one end while not simultaneously punching a hole out of its rear end had long created headaches for developers.

Techniques moved forward during 1997 and the big manufacturers were soon predicting that "beyond-DVD" discs and drives should be a reality at the start of the next century. In the event, that proved to be a little over-optimistic. However, by early 2002 a faction within the DVD Forum's Steering Committee were promoting a blue laser successor to the original DVD format - dubbed Blu-ray Disc (BD) - that was capable of providing storage capacities of up to 27GB and 50GB on single-layer and dual-layer discs respectively.

The driving force behind such huge capacities wa the emergence of multimedia applications - in relation to both high-quality digital video and audio - into the PC mainstream, coupled with the emergence of high-definition TV (HDTV), which was scheduled to debut in terrestrial broadcast systems in the USA during 2003.

However, the DVD Forum's efforts to avoid a repeat of the specification shambles the plagued the original DVD rewritable formats soon showed every indication of themselves being in a state of disarray. In the autumn of 2003, within a week of a grouping of nine members of the DVD Forum's Steering Committee - Hitachi, LG Electronics, Matsushita Electric Industrial, Pioneer, Royal Philips Electronics, Samsung Electronics, Sharp, Sony and Thomson Multimedia - announcing their support for the BD format as successor to the original DVD format, the DVD Forum itself voted to approve the use of a completely different low-bit-rate compression technology - proposed by DVD format pioneer Toshiba and NEC - renaming as "HD-DVD" the format that had hitherto been referred to as the "Advanced Optical Disc".

Although the HD-DVD format offered significantly less capacity than the Blu-ray technology, using low-bit-rate encoding technology such as MPEG-4 to store 9GB of high-definition video content onto a dual-layer DVD, the DVD Forum justified its decision on the grounds of production costs. Its similarity to the current DVD manufacturing processes makes it much less expensive to adapt current production lines for producing HD-DVDs than it would be to adapt for BD production.

While some believed that it might be possible for the HD-DVD and BD technologies to co-exist - the former being positioned as a playback format for pre-recorded HD-DVD movies and the latter as a recording format for real-time interlaced TV programs, including HDTV programming - others foresaw a battle between the rival formats similar to the "VCR" VHS/Betamax format war which raged in the decade ending in the late 1980s.

At the time the specification of each of the technologies was first disclosed, a comparison with the current DVD format looked as follows:

Format

Current generation

Next generation

DVD playback 4.7GB (single-layer disc);
650nm red laser;
MPEG-2 video compression. Blu-ray disc;
27GB (single-layer disc);
up to 50GB (dual-layer disc);
405nm blue-violet laser;
MPEG-2 video;
incompatible with DVD format.

DVD recordable 4.7GB (single-layer disc);
DVD-R (write-once);
DVD-RAM (rewritable);
DVD-RW (rewritable);
DVD+RW (rewritable);
650nm red laser;
MPEG-2 video compression. HD-DVD disc;
9GB (dual layer disc);
405nm blue-violet laser;
MPEG-4 or improved MPEG-2
with extensive pre- and post-processing;
compatible with DVD format.