28-01-2011, 01:54 PM
[attachment=8508]
By
NAVEEN KUMAR.H.V
Vth Sem MCA,4NM03MCA34
Introduction to BLU-RAY
The Blu-ray name is a combination of "blue," for the color of the laser that is used, and "ray," for optical ray.
Blu-ray is the next-generation digital video disc. It can record, store and play back high-definition video and digital audio, as well as computer data.
The "e" in "blue" was purposefully left off, according to the manufacturers, because an everyday word cannot be trademarked.
Why & What is actually BLU-RAY DISC ?
BLU-RAY DISC is a next generation digital video disc which can record , store and play back high definition video & digital audio as well as computer data.
BLU-RAY DISC comes in 2 types
* A single layer disc
* A double layer disc
These disc not only have storage capacity than
DVD’s but they also offer a new level of interactivity…
Double layer vs. Single layer disc
Double layer disc
A double layer disc is same as that of a DVD can store upto 54GB , enough to hold about 4.5 hrs of
high-definition video or more than 20 hrs of standard video.
Single layer disc
A single layer disc is roughly same size as DVD ,can hold upto
27GB of data ---that’s more than 2 hrs of high-definition video or about 13 hrs of standard video.
Working of BLU-RAY DISC !!
Discs store digitally encoded video and audio information in pits -- spiral grooves that run from the center of the disc to its edges.
A laser reads the other side of these pits -- the bumps-- to play the movie or program that is stored on the DVD.
The more data that is contained on a disc, the smaller and more closely packed the pits must be. The smaller the pits (and therefore the bumps), the more precise the reading laser must be.
DVD which uses a red laser to read and write data, Blu-Disc uses a blue laser . A blue laser has a shorter wavelength (405 nanometers) than a red laser (650 nanometers). The smaller beam focuses more precisely, enabling it to read information .
recorded in pits that are only 0.15 microns (µm) (1 micron = 10-6 meters) long -- this is more than twice as small as the pits on a DVD. Plus, Blu-ray has reduced the track pitch from 0.74 microns to 0.32 microns.
DVD vs. BLU-RAY construction
In a DVD, the data is sandwiched between two polycarbonate layers, each 0.6-mm thick. 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.
Building a BLU-RAY
The Blu-ray disc overcomes DVD-reading issues by placing the data on top of a 1.1-mm-thick polycarbonate layer.
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.
Formats of BLU-RAY
Unlike DVDs and CDs, which started with read-only formats and only later added recordable and re-writable formats, Blu-ray is initially designed in several different formats:
BD-ROM (read-only) - for pre-recorded content
BD-R (recordable) - for PC data storage
BD-RW (rewritable) - for PC data storage
BD-RE (rewritable) - for HDTV recording
Video/Audio Stream Recording
The Metadata File allows clustering the file system metadata (file mgt Information , such as file entries and directories) and improves performance for accessing multiple directories.
The files recorded in the area for metadata and database files can be read with a fewer number of seeks, reducing the response time during Play List editing and menu display, resulting in greatly improved system response.
BLU-RAY Advantages
record high-definition television (HDTV) without any quality loss
instantly skip to any spot on the disc
record one program while watching another on the disc
edit or reorder programs recorded on the disc
automatically search for an empty space on the disc to avoid recording over a program
Access the Web to download subtitles and other extra features.
Blu-ray discs are better armed than current DVDs. They come equipped with a secure encryption system -- a unique ID that protects against video piracy and copyright infringement.
Conclusion
It seems that the future holds a whole lot more than 25 to 54 GB on a single disc.
There may be a day when computers don't use hard disks , instead an optical disk such as BLU-RAY DISC might be used. This will be definitely a big revolution in computer history . Which uses ULTRAVIOLET lasers which has even shorter wavelength than the blue lasers that we are using now .
