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Well this post sent by one of our forum member helps,
"Blu-ray vs HD DVD: State of the Division
Posted Sep 19th 2005 2:10PM by Ryan Block
Filed under: Features, Home Entertainment
Well, as far as HD DVD vs. Blu-ray goes, it looks like we've pretty much passed the point of no return now; with each passing day it seems less and less likely that a compromise will be reached on a next-gen format. The ongoing peace talks between the two camps, which have been on-again, off-again for months now, seem to have finally dissolved. It's disappointing, but however you feel about the fact that the HD DVD and Blu-ray factions squandered countless chances to make it right and come together, it looks like in just a few short months they're going to be duking it out mano a mano right in our livingrooms. There may not be a lot we can do to fight back - apart from refusing to adopt either format out of sheer spite of their pigheadedness - but no matter what we might as well at least arm ourselves with the knowledge necessary to understand the nature of the situation at hand.
Here's the background:
Philips's development of the Laserdisc in 1969 yielded many of the technologies Sony carried over and adopted when they eventually partnered with way back in '79 Philips to create a little something called the CD. Both companies were hard at work together once again in the early 1990s on a new high-density disc called the MultiMedia Compact Disc (MMCD -- original name, guys), but their format was more or less abandoned in favor of Toshiba's competing Super Density Disc (SD), which had the vast majority of backers at the time, such as Hitachi, Matsushita (Panasonic), Mitsubishi, Pioneer, Thomson, and Time Warner.
The two factions cut a deal, brokered by IBM president Lou Gerstner, on a new format: DVD. Toshiba wound up on top after the dust settled in 1995/1996, and Sony and Philips, who weren't cut in on the standard (and royalties) nearly as much as they'd have liked, immediately started work on a next gen system. The Professional Disc for DATA (aka PDD or ProDATA), which was based on an optical disc system Sony had already been developing in the side, would eventually become the Blu-ray disc. Toshiba, not to be outdone by its rivals Sony and Philips, also started work on a next gen system, the Advanced Optical Disc, which eventually evolved into the HD DVD. But after thirty-five years of optical audio/video disc development we're back where we were years ago: two money-grubbing would-be standards bearers swiping at one another, threatening to wreak havoc on the consumer electronics industry. Apparently history really does repeat itself.
So here's the technical nitty gritty before we drop the graphs n' charts on you. Both Blu-ray and HD DVD use the same kind of 405nm wavelength blue-violet laser, but their optics differ in two ways. Since the Blu-ray disc has a tighter track pitch (the single thread of data that spirals from the inside of the disc all the way out -- think: grooves on a 12-inch vinyl single vs. an Elvis Costello full-length album with 40 songs), it can hold more pits -- information -- on the same size disc as HD DVD even with a laser of the same wavelength.
The differing track pitch of the Blu-ray disc makes its pickup apertures differ, however -- 0.65 for HD DVD vs. 0.85 for Blu-ray -- thus also making the two pickups technically incompatible despite using the same type of lasers. HD DVD discs also have a different surface layer (the clear plastic layer on the surface of the data -- the part that collects all your fingerprints and scratches) from Blu-ray discs. HD DVD use a 0.6 mm-thick surface layer, the same as DVD, while Blu-ray has a much smaller 0.1mm layer, which enables the laser to focus at that 0.85 aperture.
Herein lies the issues associated with the higher cost of Blu-ray discs. This thinner surface layer is what makes the discs cost more; because Blu-ray discs do not share the same surface layer thickness of DVDs, costly production facilities must be modified or replaced in order to produce the discs. A special hard coating (Durabis) must also be applied to Blu-ray discs to ensure they're sufficiently resilient to protect the data that's a mere 0.1mm beneath the surface -- this also drives the cost up. The added benefit of keeping the data layer closer to the surface, however, is more room for extra layers, and way more potential data than HD DVD.
Still with us? No? Blu-ray discs are more expensive, but hold more data -- there, that's all.
So now that you know why Blu-ray discs cost more and why Sony / Philips and Toshiba are all harshing on one another so much, we can get to the really important stuff: the numbers and who's supporting who.
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