How BLU-RAY works

How BLU-RAY works

A Blu-ray drive looks and works in
traditionally the same way as any other
optical drive. The difference is that
Blu-ray drives use a violet-blue laser to
read data from an optical drive media
rather then the infrared light that is used
by CDs and red laser light used by DVD
writers. The violet-blue color falls into
the higher frequency segment in the
visible spectrum of light, thus resulting
in a lower wavelength (refer to box).
The wavelength of the laser used in
Blu-ray drives is 405 nm. To put it into
perspective, a CD drive uses an infrared
laser operating at a wavelength of
780 nm while a DVD drive uses a red laser
operating at a wavelength of 650 nm.
So, as we can see, using a light source
that has a lower wavelength causes a
smaller laser beam. This is advantageous
because it can focus better at a point on
the media surface from a ?xed distance
as the wave travels faster and hits the
surface before it disperses. Thus the
light ray used in a Blu-ray drive is more
accurate in pinpointing a particular
area on the media surface. As the
focusing capability gets ?ner, media
manufacturers can increase the track
pitch (refer to box) on the media thus
increasing the media’s storage capacity.
How much data can you fit on a Blu-ray disc?

A single-layer disc can hold 25GB.
A dual-layer disc can hold 50GB.

To ensure that the Blu-ray Disc format is easily extendable
(future-proof) it also includes support for multi-layer discs, which should allow
the storage capacity to be increased to 100GB-200GB (25GB per layer) in
the future simply by adding more layers to the discs.

How much video can you fit on a Blu-ray disc?

Over 9 hours of high-definition (HD) video on a 50GB disc.
About 23 hours of standard-definition (SD) video on a 50GB disc.
What video codecs will Blu-ray support?

[black]MPEG-2 - enhanced for HD, also used for playback of DVDs and HDTV
recordings.
MPEG-4 AVC - part of the MPEG-4 standard also known as H.264 (High
Profile and Main Profile).
SMPTE VC-1 - standard based on Microsoft's Windows Media Video (WMV)
technology.

Please note that this simply means that all Blu-ray players and
recorders will have to support playback of these video codecs, it will still
be up to the movie studios to decide which video codec(s) they use for
their releases.

What audio codecs will Blu-ray support?

[black]Linear PCM (LPCM) - offers up to 8 channels of uncompressed
audio.
Dolby Digital (DD) - format used for DVDs also known as AC3, offers
5.1-channel surround sound.
Dolby Digital Plus (DD+) - extension of DD, offers increased bitrates
and 7.1-channel surround sound.
Dolby TrueHD - extension of MLP Lossless, offers lossless encoding of
up to 8 channels of audio.
DTS Digital Surround - format used for DVDs, offers 5.1-channel
surround sound.
DTS-HD - extension of DTS, offers increased bitrates and up to 8
channels of audio.

Please note that this simply means that all Blu-ray players and
recorders will have to support playback of these audio codecs, it will still
be up to the movie studios to decide which audio codec(s) they use for
their releases.
Who developed Blu-ray?

The Blu-ray Disc format was developed by the Blu-ray Disc
Association (BDA), a group of leading consumer electronics, personal computer
and media manufacturers, with more than 170 member companies from all
over the world. The Board of Directors currently consists of:

Apple Computer, Inc.
Dell Inc.
Hewlett Packard Company
Hitachi, Ltd.
LG Electronics Inc.
Matsushita Electric Industrial Co., Ltd.
Mitsubishi Electric Corporation
Pioneer Corporation
Royal Philips Electronics
Samsung Electronics Co., Ltd.
Sharp Corporation
Sony Corporation
TDK Corporation
Thomson Multimedia
Twentieth Century Fox
Walt Disney Pictures
Warner Bros. Entertainment