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HD DVD shares the 12cm diameter and 1.2mm thickness of the current generation of DVD discs, yet is able to deliver eight hours of High Definition video on a dual-layer, single-sided disc. Enhanced interactivity, multi-media functions, secure AACS content protection and the capacity to store ten thousand average MP3 tracks on one disc means that the HD DVD format matches the real-world needs of today's consumer market. For the IT industry, a double-sided HD DVD-R disc can hold up to 30GBytes of data. For replicators, there is the reassurance that today's DVDs can be produced on tomorrow's HD DVD lines.
Today's DVD is a widely accepted and very reliable data storage and delivery system. The 1.2mm thick disc has the data placed in the middle of a protective outer layer of transparent plastic. HD DVD has built on this tried and trusted format by adopting the same physical disc parameters.
As a result, the transition is a relatively simple matter for equipment manufacturers and disc replicators alike. In tests, an HD DVD production line has been changed over to conventional DVD replication in under five minutes. No other disc structure could offer such evolutionary compatibility, underscoring the advisability of this approach. By using a blue-violet laser with a numerical aperture of 0.65 for the lens, the usable spot diameter may be reduced, compared to the current red laser of DVD. As a consequence, the potential data density on the disc is increased. Coupled with higher rotational speed, this allows the maximum data transfer rate to be over three times DVD, at 36.55Mbps. The highest quality HDTV [1920x1080] is supported, along with all recognized subsets through SDTV and down to CIF [320x240]. Additionally, streaming Internet video may be synchronized with pre-recorded content.
