Blu Ray Discs-Part 2

Disc Structure and Reading Mechanism:

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.

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. 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.

THE HARD COATING TECHNOLOGY MAKES THE BRDs PRACTICALLY SCRATCH RESISTANT!!!!!!!!!!!!!!!!!!!!!!!!!


Recording speed:

Drive Speed

Date Rate

Mbit/s

Data Rate

MB/s

Write time for

Single Layer

Blu-Ray Disc(mins)

Double Layer

1x

36

4.5

90

180

2x

72

9

45

90

4x

144

18

23

45

6x

216

27

15

30

8x *

288

36

12

23

12x *

432

54

8

15

* Theoretical
Codecs:

The BD-ROM specification mandates certain codec compatibilities for both hardware decoders (players) and the movie-software (content).

For video, all players are required to support MPEG-2, H.264/AVC, and SMPTE VC-1. MPEG-2 is the codec used on regular DVDs, which allows backwards compatibility. H.264/AVC was developed by MPEG and VCEG as a modern successor of MPEG-4. VC-1 is another MPEG-4 derivative codec mostly developed by Microsoft.

For audio, BD-ROM players are required to support Dolby Digital AC-3, DTS, and linear PCM. Players may optionally support Dolby Digital Plus, and lossless formats Dolby TrueHD and DTS-HD Master Audio.

Region Codes:

Region code Area

A(Orange) Americas; East and Southeast Asia; U.S. territories; Bermuda
B(Green) Africa, Europe, Oceania; Middle East; Kingdom of the Netherlands; British overseas territories, French territories; Greenland.
C(Voilet) Central and South Asia; Mongolia, Russia, and People’s Republic of China.

Digital Rights Management:

Digital rights management (DRM) is an umbrella term that refers to access control technologies used by publishers and copyright holders to limit usage of digital media or devices. It may also refer to restrictions associated with specific instances of digital works or devices. DRM overlaps with software copy protection to some extent, however the term “DRM” is usually applied to creative media (music, films, etc.) whereas the term “copy protection” tends to refer to copy protection mechanisms in computer software.

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


Competitors for BRDs:

Blu-ray and HD-DVD are the two major competitors in the market, but there are other contenders, as well. Warner Bros. Pictures has developed its own system, called HD-DVD-9. This system uses a higher compression rate to put more information (about two hours of high-definition video) on a standard DVD. Taiwan has created the Forward Versatile Disc (FVD), an upgraded version of today’s DVDs that allows for more data storage capacity (5.4 GB on a single-sided disc and 9.8 GB on a double-sided disc). And China has introduced the Enhanced Video Disc (EVD), another high-definition video disc.

There are also professional versions of the blue laser technology. Sony has developed XDCAM and ProData (Professional Disc for Data). The former is designed for use by broadcasters and AV studios. The latter is primarily for commercial data storage (for example, backing up servers).

FAQ next time

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