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  Blu-ray vs. HD DVD: The Format Wars

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HD DVD Technology (continued)

The Disc

HD DVDs use the same blue laser technology as Blu-ray Discs. This is why HD DVDs provide more memory capacity than DVDs despite of its other similarities.

The difference between Blu-ray and HD DVD is the size of the aperture used on the optical pick-up head inside drives and players. Blu-ray uses a 0.85 aperture whereas HD DVDs only use a 0.65 aperture. Finally compare that to current DVDs’ 0.6 aperture. The reason these are different is because of the surface layer of the actual discs. Their thickness limits the effectiveness of the laser due to optical effects.

HD DVDs have a thickness of 0.6mm, the same as current DVDs, which is why the aperture is only marginally larger, thus limiting the discs capacity. BDs have a surface that is only 0.1mm thick, which reduces optical illusions, and enables the larger aperture to be used.

Security

HD DVD-ROMs will include protection which is expected to be produced by AACS LA. This technology, called AACS, will also be included on BDs. AACS is backed by companies supporting both Blu-ray and HD DVD technologies. AACS uses similar security measures as CSS, which failed in the past, thus raising concerns regarding its effectiveness. The technology was in fact voted most likely to fail by IEEE, the largest organization in the world for ‘the advancement of technology related to electricity’.

The difference between CSS and AACS is that instead of having group decryption keys that were allocated to a particular player model, every player will have an individual ‘key’ used in a broadcast encryption scheme. This allows licensors to identify individuals who have leaked their keys. They can then disable a particular player’s functionality with future media as well as carry out legal action against a specific individual.

HD DVDs will also incorporate digital watermarking to protect their products. Watermarking is a process of hiding a copyright notice within digital media that will prevent duplication or reproduction of media without authorization.

Applications

HD DVDs will include the same compression formats as BDs; MPEG-4 AVC, VC-1, and MPEG-2. MPEG-2 TS has been used to allow direct recording from HDTV broadcasts without picture quality loss. The current data transfer rate is 36.55Mbps. It will of course be backwards compatible with DVD and CD technology, this is where its appeal lies, however that does not mean Blu-ray technology is not backwards compatible.

The first lot of HD DVD players is expected to arrive in March 2006. Microsoft did not include a HD DVD player in their Xbox 360, but is said to be releasing an external add-on drive late in 2006. There are also many movie studios who will be releasing movies on both HD DVD and BD formats by the end of this year.



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