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DOUBLE LAYER MEDIA

Double layer media work by spinning the disc in the opposite direction to read information encoded on a second layer of data. This second layer is readable because the first layer is actually semi-transparent. Unfortunately, dual or double layered DVD media is not always backwards compatible, and many older players will experience difficulties.

Even when double layer media is read there will be a slight pause as the laser head and other internal mechanism transitions from one layer to the other. But compatibility issues were, and remain, the paramount concern for DVD enthusiasts. After all, the general home user doesn't want anything complicated, and competing formats do just that - muddy the waters by offering so many options.

Format wars are nothing new when it comes to technology hardware and software and are not relegated solely to double layer media. Even with well over a decade in the market, DVDs can still occasion some confusion for the common consumer of home electronics. It would seem, however, that DVD format wars are now a thing of the past, given HD-DVD’s recent abdication of the market to Blu-ray Disc. This fifth in a series of articles examining all things DVD will continue the survey of the discontinued HD-DVD format that was begun with the last article.

The now-defunct HD-DVD Promotion Group had started life as a rebellious outgrowth of the earlier DVD Forum. The DVD Forum was a consortium of industry insiders with a mission of promotion of and advocacy for the DVD format. When the march of technological progress saw the formation of cliques around different formats, a schism was caused whereby member companies coalesced around new organizations dedicated to specific formats. The HD-DVD Promotion Group was one such outgrowth of the split, in reaction to an earlier one, the Blu-ray Disc Association.

Blu-ray Disc was developed by Sony while continuing research into the laser technology that makes DVDs possible. Though virtually identical to a standard DVD today, at the time of their introduction Blu-ray Discs required an expensive housing caddy in addition to special players that would accept them. The DVD Forum eventually decided on a proposal endorsed by Warner Brothers, along with several other motion picture studios. This was to have been dual-layer DVD-9, the first double layer media for home use. But cliques were formed around different formats anyway, with Toshiba and NEC themselves pursuing a format then called Advanced Optical Disc, which in time came to be adopted by the DVD Forum as HD-DVD.

An attempt was made to avoid a costly format war, reminiscent of Betamax versus VHS back in the late ’70s and early ’80s between Sony and Panasonic, the Blu-ray Disc Association and the DVD Forum tried to negotiate a compromise. As we now know, it was not successful. It’s debatable whether a compromise could ever have been possible. Aside from the aforementioned matter of physical incompatibility, an additional deal-breaker had been each side’s insistence on different software platforms to govern interactivity: the Blu-ray Disc Association favored one based on Sun Microsystems’ Java language, while HD-DVD advocates wanted Microsoft’s iHD (later renamed “HDi").

With neither side able to compromise enough and each side comprised of important industry heavy-weights, the stage for a costly format war was set.