Saturday, May 9, 2009

What is Blu-ray?

Blu-ray disc or commonly called as BD is the name of the next generation optical media disc format that was specifically designed to support the latest high definition video and audio technologies.

The Blu-ray Disc Association (BDA), a group representing electronics, computer hardware and motion picture production companies, introduced Blu-ray in 2006.

Blu-ray discs can hold large quantities of high-definition video and audio, computer data and other digital content. The capacity of single-layer BD is 25 GB while that of normal DVD is just 4.7 GB. That means, a Blu-ray Disc can hold as much data as 5.5 times that of DVD.

Blu-ray Disc Logo
Why not Blue-ray?

The name Blu-ray was derived from the combination of blue the color of the laser in use, and ray meaning travel path of light. However, Blu-ray Disc Association decided to leave “e” behind of “blue” being a common word that cannot be trademarked.

How Blu-ray Works?

Blu-ray disc’s working technology is almost similar to that of DVDs. The major difference in BD is that the tracks are narrow and the pits are very close to each other thus enabling BD to pack more data in a similar sized disc.
Blu-ray, DVD, CD Lasers
In order to read & write data at these tiny sizes, BD employs the laser beam of lowest wavelength. Thus, BD uses the Blue-Violet laser that has the shortest wavelength among all lasers. When this laser creates small pits in the tracks (circular paths), data is stored. The pits represent the binary zero and one. Thus by packing more pits in narrow tracks, Blu-ray discs can hold up to 25GB of data in single layer.

What makes Blu-ray different from other optical media formats?

Disc Capacity

As earlier described, BD discs can store more than any other optical disc format. Single layer BD (Blu-ray) Disc can hold 25GB while double layer Disc can store 50GB.

Theoretically, Blu-ray disc of multiple layers can hold up to 200GB of data. However, the maximum capacity achieved so far is 100 GB.
TDK 100 GB BD
Higher data capacity also ensures the disc is future proof that it would even support future high bit rate or more resolution video / audio formats that may need more storage space.

Data Transfer Rates - Blu-ray Transfers More

Blu-ray offers an amazing 54Mb/s data transfer rate for raw data and 40Mb/s for video. This means Blu-ray is the best choice for high data rate usage such as high definition content. Here is how:

For a movie at 1080p resolution containing 7.1 channel HD Dolby or DTS HD signal, you will need at least 39Mb/s data transfer rate. This means, these latest HD format can only work in Blu-ray as only Blu-ray discs offer such a high data transfer rate of over 40Mb/s. The former rival HD-DVD format can only deliver 33 Mb/s.

Higher data rate also means faster file transfers. Thus, BD offers better capacity and faster files transfers than any other optical media format invented.

Blu-ray’s Hard-Coated Surface Prevents Scratch

As the Blu-ray Disc employs high-density laser precise recording, BD Discs require an added hard coating technology called Durabis, which will protect the disc from scratches and fingerprints. Durabis coating discharges static electricity, which prevents it from gathering dust.

Blu-ray Security is Tough to Crack

Even though this is not always good for consumers, this is an important point Sony has for the movie studios. Movie studios want their content locked from the pirates and BD’s security and encryption features just help them do it in the most advanced way.

Blu-ray Disc Players

Blu-ray has three layers of protection called AACS, BD+ and ROM mark.

AACS

The Advanced Access Content System (AACS) is digital rights management feature that prevents any un-authorized copying of content from BD discs.

AACS uses an encryption technology called Advanced Encryption Standard (AES). AACS is more advanced than earlier DRM used in DVDs. The difference with AACS is that each licensed player is given a unique set of decryption keys that licensors can “revoke” whenever they feel it has been compromised. By revoking a decryption key, the particular player will not be able to play any future HD content. Thus discouraging any attempt to decrypt the key.

BD+

BD+ is a safeguard against future cracks and hacks. It is a kind of and advanced DRM. Every authorized player will have a BD+ virtual machine that will decode the disc content to correct version. The advantage of BD+ is that it is dynamic and hence content providers can change the security feature whenever they wish. Thus, different Discs will have different encryption and therefore no single fix would help them play all BD discs.

ROM Mark

ROM mark was designed to prevent unwanted duplication of BD Discs. ROM Mark helps to create unique Discs that cannot be copied using software. This BD Discs will have a unique ID that are created with a specific BD licensed writer drive. No licensed BD players will work unless the inserted disc has a ROM mark. Therefore, without specialized equipments, you cannot copy a ROM Marked BD disc.

What are the different Blu-ray Disc formats?

Blu-ray discs are available in four different version. Here are they:

  • BD-ROM - Blu-ray Read Only. Version for Software companies and Movie studios.
  • BD-R - One time recordable version for computer users.
  • BD-RW - For computer users. This disc is re-writable.
  • BD-RE - A specialized version for HDTV recording.

This BD-RE disc offers editing functionality and time shifting features when recorded through a compatible Blu-ray HDTV recorder.

What are the Audio / Video Formats Supported by Blu-ray?

Blu-ray supports almost all high-resolution audio / video formats. In fact, Blu-ray was designed for just for HD content. Here is the full technical specification of Blu-ray disc.

Blu-ray Technical Specification:

Laser Wavelength: 405Nm
Storage Capacity: 25GB (Single Layer), 50GB (Dual Layer), 100 GB (4 Layers)
Playback time: 12hrs (DVD Quality), 3.5 hrs (HD Quality) on a single layer disc
Supported Video Codecs: MPEG-4 AVC (H.264) / VC-1 / MPEG-2
Supported Audio Codecs: Lossy - Dolby Digital / DTS / MPEG Audio & Lossless - Linear PCM, Dolby TRUE HD, DTS HD
Data Transfer Rate: 54 Mb/s RAW Data / 40Mb/s for Video with audio and subtitles.
Security Features: AACS, BD+, ROM Mark
Protective Hard Coating: Durabis

For more information on Blu-ray technology and new releases, visit the following websites:

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