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It is the next generation secondary storage medium, that has a very high storage capacity and reliability.
It allows the storage of high definition(HD) content.
It also provide increased throughput over regular DVDs.
FIRST GENERATION -Compact Disc (CD)
The first CD’s were meant for audio, and
later on the CD-ROM came into place giving
us 650/700 Mb of space per disc .
CD Uses 780 nanometer red laser.
DVD (Digital Versatile Disc)
DVD was introduced as an enormous upgrade of capacity, giving enough room (4.7 Gigabytes) for high quality sound and multimedia on a single disc.
DVD uses a 650 nanometer red laser.
There are also 2 layers for even more capacity(8.5 GB). This gives plenty of room to put an entire movie on a single DVD.
Blu-ray, also known as Blu-ray Disc (BD), is the
name of a next-generation optical disc format jointly
developed by the Blu-ray Disc Association (BDA), a
group of the world's leading consumer electronics,
personal computer and media manufacturers.
The format was developed to enable recording,
rewriting and playback of high-definition video (HD),
as well as storing large amounts of data.
.
The format offers more than five times the storage
capacity of traditional DVDs and can hold up to 25GB
on a single-layer disc and 50GB on a dual-layer disc.
Blu-ray Disc format is
easily extendable, it
also includes support
for multi-layer discs,
which should allow
the storage capacity to
be increased to
100GB-250GB (25GB
per layer) in the future
simply by adding more
layers to the discs.
BD-ROM - read-only format for distribution of HD
movies, games, software, etc.
BD-R - recordable format for HD video recording and PC
data storage.
BD-RW - rewritable format for PC data storage.
BD-RE (rewritable) - for HDTV recording
About 9 hours of high-definition (HD) video can be stored
on a 50 GB disc.
About 23 hours of standard-definition (SD) video can be
stored on a 50 GB disc.
Physical size -12 cm, single sided
12 cm, double sided
8 cm, single sided
8 cm, double sided
The Blu-ray Disc system uses a blue-laser operating at a
wavelength of 405 nm, similar to the one used for HD
DVD, to read and write data. Conventional DVDs and
CDs use red and infrared lasers at 650 nm and 780 nm
respectively
It possible to focus the laser spot with even greater
precision. This allows data to be packed more tightly
and stored in less space, so it's possible to fit more data
on the disc even though it's the same size as a
CD/DVD.
.
Blu-ray read data at 36Mb/s on single speed. where DVD
read data at 10Mb/s.
Blu-ray will require less recording power and lower disc
rotation speed than DVD and HD-DVD to achieve the
same data transfer rate.
It records high-definition television (HDTV) without any quality loss .
Capability to skip to any spot on the disc instantly.
Capable of recording one program while watching another on the disc.
create playlists.
automatically search for an empty space on the disc to avoid recording over a program.
the inclusion of a Java Virtual Machine as well as internet connectivity in BD devices will allow updates to Blu-ray Discs , adding content such as additional subtitle languages and promotional features that are not included on the disc .
The smaller beam focuses more precisely, enabling it to read information recorded in pits that are only 0.15 microns(µm) long -- this is more than twice as small as the pits on a DVD.
Blu-ray has reduced the track pitch from 0.74 microns to 0.32 microns.
The smaller pits, smaller beam and shorter track pitch together enable a single-layer Blu-ray disc to hold more than 25 GB of information
Traditional DVDs are built by injection molding the two 0.6-mm discs ,between which the recording layer is sandwiched.
The two discs are molded.
The recording layer is added to one of the discs.
The two discs are glued together.
Having a polycarbonate layer on top of the data can cause a
problem called birefringence, in which the substrate layer
refracts the laser light into two separate beams. If the beam
is split too widely, the disc cannot be read.
If the DVD surface is not exactly flat, and is therefore not
exactly perpendicular to the beam, it can lead to a problem
known as disc tilt, in which the laser beam is distorted
Blu-ray discs only do the injection-molding process on a single 1.1-mm disc, which reduces cost.
Because the data is closer to the surface, a hard coating is placed on the outside of the disc to protect it from scratches and fingerprints.
Having the data on top prevents birefringence and therefore prevents readability problems. And, with the recording layer sitting closer to the objective lens of the reading mechanism, the problem of disc tilt is virtually eliminated.
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.
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.
Blu-ray drives should be capable of reading and writing
CDs, DVDs, and Blu-ray Discs.
It consist of 2 Laser diodes and 2 Lenses.
HD-DVD(High Definition DVD)
It also uses blue laser to read and write data.
Storage capacity is less compared to BD.
BD has a hard Coating.
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