Blue Ray

For high-definition movies a much higher data rate is needed than for standard
definition. With the BD format’s choices for both NA and wavelength we have been able to
realize a format with 5X higher data rate while only doubling the rotation rate of DVD-ROM
discs. The following numbers offer a comparison: Data bit length: 111.75 nm (25GB) (267
nm for DVD) Linear velocity: 7.367 m/s (Movie application) (3.49 m/s for DVD). User data
transfer rate: 53.948 Mbit/s (Movie application) (10.08 Mbps for DVD)
The BD system has the potential for future higher speed drives.
The BD-RE (rewritable) standard is now available; to be followed by the BD-R
(recordable) and BD-ROM formats in mid-2004, as part of version 2.0 of the Blu-ray specifications.
BD-ROM pre-recorded media are to be available by late 2005. Looking further ahead in time, Blu-ray
Discs with capacities of 100GB and 200GB are currently being researched, with these capacities
achieved by using four and eight layers respectively.
3.4 CODECS
The BD-ROM format will likely include 3 codecs: MPEG-2 (the standard used for
DVDs), MPEG-4's H.264/AVC codec, and VC-1 based on Microsoft's Windows Media 9 codec.
The first codec only allows for about two hours of storage on a single layer Blu-ray Disc, but with the
addition of the latter two more advanced codecs, a single-layer disc can hold almost four hours. Highdefinition
MPEG-2 has a data rate of about 25Mbps, while the latter two have data rates of about
I5Mbps for video and 3Mbps for audio.
BD-RE (and by extension BD-R) does not currently support any advanced
codecs beyond MPEG-2. Because MPEG-2 is currently used to broadcast HDTV, recorders write
this HD stream directly to a disc. Since there are no consumer level recorders capable of real-time