Blue ray Technical Specification

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Blue ray technical specifications

Standard disc size: 12 cm

• Single layer capacity 25 GB / 23866 MB / 25025314816 Bytes
• Dual layer capacity 50 GB / 47732 MB / 50050629632 Bytes

Mini disc size: 8 cm

• Single layer capacity 7.8 GB / 7430 MB / 7791181824 Bytes
• Dual layer capacity 15.6 GB / 148605 MB / 15582363648 Bytes

High-definition video may be stored on Blu-ray ROM discs with up to 1920×1080 pixel resolution at up to 60 frames per second interlaced or 24 frames per second progressive.

Laser and optics

Blu-ray Disc uses a “blue” (technically violet) laser operating at a wavelength of 405 nm to read and write data. Conventional DVDs and CDs use red and near infrared lasers at 650 nm and 780 nm respectively.

The blue-violet laser’s shorter wavelength makes it possible to store more information on a 12 cm CD/DVD sized disc. The minimum “spot size” on which a laser can be focused is limited by diffraction, and depends on the wavelength of the light and the numerical aperture of the lens used to focus it. By decreasing the wavelength, increasing the numerical aperture from 0.60 to 0.85 and making the cover layer thinner to avoid unwanted optical effects, the laser beam can be focused to a smaller spot. This allows more information to be stored in the same area. For Blu-ray Disc, the spot size is 580 nm. In addition to the optical improvements, Blu-ray Discs feature improvements in data encoding that further increase the capacity. (See Compact Disc for information on optical discs’ physical structure.)

Hard-coating technology

Since the Blu-ray Disc data layer is closer to the surface of the disc, compared to the DVD standard, it was at first more vulnerable to scratches.[10] The first discs were housed in cartridges for protection.

TDK was the first company to develop a working scratch protection coating for Blu-ray Discs. It was named Durabis. In addition, both Sony and Panasonic’s replication methods include proprietary hard-coat technologies. Sony’s rewritable media are spin-coated with a scratch-resistant and antistatic coating. Verbatim’s recordable and rewritable Blu-ray Discs use their own proprietary hard-coat technology called ScratchGuard.

Recording speedDrive speed Data rate Write time for Blu-ray Disc (minutes)
Mbit/s MB/s Single Layer Dual Layer
1× 36 4.5 90 180
2× 72 9 45 90
4× 144 18 23 45
6× 216 27 15 30
8×* 288 36 12 23
12×** 432 54 8 15

* On August 8, 2008, Japanese electronics company Buffalo announced that it will ship the first 8x Blu-ray burners in Japan starting from September 2008.[52] On September 22, 2008, Buffalo announced one internal and one external 8x Blu-ray burners for the United States, to be released the same month.[53] The following day Sony announced the BWU-300S, an internal 8x Blu-ray burner for the United States.[54]

** Theoretical

Software standards

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/MPEG-4 AVC, and SMPTE VC-1.[55] MPEG-2 is the codec used on regular DVDs, which allows backwards compatibility. MPEG-4 AVC was developed by MPEG and VCEG. VC-1 is a codec that was mainly developed by Microsoft. BD-ROM titles with video must store video using one of the three mandatory codecs. Multiple codecs on a single title are allowed.

The choice of codecs affects the producer’s licensing/royalty costs, as well as the title’s maximum runtime, due to differences in compression efficiency. Discs encoded in MPEG-2 video typically limit content producers to around two hours of high-definition content on a single-layer (25 GB) BD-ROM. The more advanced video codecs (VC-1 and MPEG-4 AVC) typically achieve a video runtime twice that of MPEG-2, with comparable quality.

MPEG-2 was used by many studios, including Paramount Pictures (which initially used the VC-1 codec for HD DVD releases) for the first series of Blu-ray discs that were launched throughout 2006. Modern releases are now often encoded in either MPEG-4 AVC or VC-1, allowing film studios to place all content on one disc, reducing costs and improving ease of use. Using these codecs will also free many GBs of space for storage of bonus content in HD (1080i/p) as opposed to the SD (480i/p) typically used for most titles. Some studios (such as Warner Bros.) have released bonus content on discs encoded in a different codec than the main feature title; for example the Blu-ray Disc release of Superman Returns uses VC-1 for the feature film and MPEG-2 for bonus content (presumably because VC-1 encoding tools were not sophisticated enough to support the workload of all that bonus content and thus would be too difficult to use).[citation needed] Today, Warner and other studios typically provide bonus content in the video codec that matches the feature.

For audio, BD-ROM players are required to support Dolby Digital, DTS, and linear PCM. Players may optionally support Dolby Digital Plus and DTS-HD High Resolution Audio, as well as lossless formats Dolby TrueHD and DTS-HD Master Audio.[56] BD-ROM titles must use one of the mandatory schemes for the primary soundtrack. A secondary audiotrack, if present, may use any of the mandatory or optional codecs.

For users recording digital television programming, the recordable Blu-ray Disc standard’s initial data rate of 36 Mbit/s is more than adequate to record high-definition broadcasts from any source (IPTV, cable/satellite, or terrestrial). BD-Video movies have a maximum data transfer rate of 54 Mbit/s, a maximum AV bitrate of 48 Mbit/s (for both audio and video data), and a maximum video bitrate of 40 Mbit/s. This compares to HD DVD movies which have a maximum data transfer rate of 36 Mbit/s, a maximum AV bitrate of 30.24 Mbit/s, and a maximum video bitrate of 29.4 Mbit/s.[57]

Java software support

At the 2005 JavaOne trade show, it was announced that Sun Microsystems’ Java cross-platform software environment would be included in all Blu-ray Disc players as a mandatory part of the standard. Java is used to implement interactive menus on Blu-ray Discs, as opposed to the method used on DVD video discs, which uses pre-rendered MPEG segments and selectable subtitle pictures, which is considerably more primitive and rarely seamless. Java creator James Gosling, at the conference, suggested that the inclusion of a Java Virtual Machine as well as network connectivity in some BD devices will allow updates to Blu-ray Discs via the Internet, adding content such as additional subtitle languages and promotional features that are not included on the disc at pressing time. This Java Version is called BD-J and is a subset of the Globally Executable MHP (GEM) standard. GEM is the worldwide version of the Multimedia Home Platform standard. Most Blu-ray Discs which have BD-J menus do not allow a Blu-ray Disc player to automatically resume a movie from the point where the movie was stopped.

Region codes

Regions for Blu-ray standard
A: East Asia (except Mainland China and Mongolia), Southeast Asia, the Americas and their dependencies.
B: Africa, Southwest Asia, Europe (except Russia), Oceania and their dependencies.
C: Central Asia, East Asia (Mainland China and Mongolia only), South Asia, central Eurasia (including Russia) and their dependencies.

Blu-ray Discs may be encoded with a region code, intended to restrict the area of the world in which they can be played, similar in principle to the DVD region codes, although the used geographical regions differ. Blu-ray Disc players sold in a certain region may only play discs encoded for that region. This is primarily used for market segmentation, or price discrimination, but it also allows motion picture studios to control the various aspects of a release (including content and release date) according to the region. Discs may also be produced without region coding, so they can be played on all devices. The countries of the major Blu-ray manufacturers (Japan, Malaysia, South Korea, etc.) are in the same region as the Americas. As of late 2008, almost 70% of all released discs were region-free.[59]

Major studios have different region coding policies. Paramount Pictures and Universal Studios have released all of their titles region free.[60][61] Sony Pictures and Warner Bros. have released most of their titles region free, but titles released by Warner’s New Line division were, initially, region-coded but subsequently have been released without being locked. Titles released by other labels on behalf of New Line are still subject to some region locking.[62][63] Lionsgate and Walt Disney Pictures have released a mix of titles that were region free and region coded.[64][65] 20th Century Fox has released all but eleven of their titles region coded.[66]

In the Blu-ray region coding system, the United States is placed in region A while regions B and C are used for countries which can experience localization delays before U.S. titles are officially released. The opposite, though, is sometimes true and a few new titles such as Harry Potter and the Goblet of Fire and Running Scared were released in certain European countries before the U.S. release.[67] In response to the DVD region system, multi-region and region-free DVD players became dominant in certain markets; certain Blu-ray player models have been modified to allow for playback of Blu-ray and DVD discs with any region code.[68]

Digital rights management

The Blu-ray Disc format employs several layers of digital rights management.[69][70]

AACS decryption process

AACS

Advanced Access Content System (AACS) is a standard for content distribution and digital rights management. It is developed by AS Licensing Administrator, LLC (AACS LA), a consortium that includes Disney, Intel, Microsoft, Panasonic, Warner Bros., IBM, Toshiba and Sony.

Since appearing in devices in 2006, several successful attacks have been made on the format. The first known attack relied on the trusted client problem. In addition, decryption keys have been extracted from a weakly protected player (WinDVD). Since keys can be revoked in newer releases,[71] this is only a temporary attack and new keys must continually be discovered in order to decrypt the latest discs. This cat-and-mouse game has gone through several cycles and as of August 2008 all current AACS decryption keys are available on the Internet.

BD+

BD+ was developed by Cryptography Research Inc. and is based on their concept of Self-Protecting Digital Content.[72] BD+ is effectively a small virtual machine embedded in authorized players. It allows content providers to include executable programs on Blu-ray Discs. Such programs can:[69]
examine the host environment, to see if the player has been tampered with. Every licensed playback device manufacturer must provide the BD+ licensing authority with memory footprints that identify their devices.
verify that the player’s keys have not been changed.
execute native code, possibly to patch an otherwise insecure system.
transform the audio and video output. Parts of the content will not be viewable without letting the BD+-program unscramble it.

If a playback device manufacturer finds that its devices have been hacked, it can potentially release BD+-code that detects and circumvents the vulnerability. These programs can then be included in all new content releases.

The specifications of the BD+ virtual machine are available only to licensed device manufacturers. A list of licensed commercial adopters is available from the BD+ website.

The first titles using BD+ were released in October 2007. Versions of the BD+ protection have been circumvented by various versions of the AnyDVD HD program. Another program known to be capable of circumventing the BD+ protection is DumpHD (versions 0.6 and above and along with some supporting software), which is available with freeware license and known to be compatible both with Windows and various Linux distributions.[73]

BD-ROM Mark

BD-ROM Mark is a small amount of cryptographic data that is stored separately from normal Blu-ray Disc data. Bit-by-bit copies that do not replicate the BD-ROM Mark are impossible to decode.[citation needed] A specially licensed piece of hardware is required to insert the ROM-mark into the media during replication. Through licensing of the special hardware element, the BDA believes that it can eliminate the possibility of mass producing BD-ROMs without authorization.[citation needed]

Player profiles

The BD-ROM specification defines four Blu-ray Disc player profiles, including an audio-only player profile (BD-Audio) that does not require video decoding or BD-J.[74] All three of the video based player profiles (BD-Video) are required to have a full implementation of BD-J, but with varying levels of hardware support.Feature BD-Audio BD-Video
Grace Period [d] Bonus View BD-Live[e]
Profile 3.0 [c] Profile 1.0 Profile 1.1 Profile 2.0
Built-in persistent memory No 64 KB 64 KB 64 KB
Local storage capability[a] No Optional 256 MB 1 GB
Secondary video decoder (PiP) No Optional Mandatory Mandatory
Secondary audio decoder[b] No Optional Mandatory Mandatory
Virtual file system No Optional Mandatory Mandatory
Internet connection capability No No No Mandatory

^ a This is used for storing audio/video and title updates. It can either be built in memory or removable media, such as a memory card or USB flash memory.
^ b A secondary audio decoder is typically used for interactive audio and commentary.
^ c Profile 3.0 is a separate audio only player profile. The first Blu-ray Disc album to be released was Divertimenti by record label Lindberg Lyd and it has been confirmed to work on the PS3.
^ d Is also known as Initial Standard profile.
^ e Is also known as Final Standard profile.

On November 1, 2007, the Grace period Profile was superseded by Bonus View as the minimum profile for new BD-Video players released to the market.[77] When Blu-ray Disc software authored with interactive features dependent on Bonus View or BD-Live hardware capabilities are played on Profile 1.0 players they will be able to play the main feature of the disc but some extra features may not be available or may offer limited capability.[78]

The biggest difference between Bonus View and BD-Live is that BD-Live requires the Blu-ray Disc player to have an internet connection (usually via a standard Ethernet RJ-45 network port) to access internet based content. BD-Live features have included internet chats, scheduled chats with the director, internet games, downloadable featurettes, downloadable quizzes, and downloadable movie trailers.[79][80][81] Note that while some Bonus View players may have an Ethernet port, these are used for firmware updates and are not used for internet based content. In addition, to handle this content, Profile 2.0 also requires more local storage.

With the exception of the LG-BH100, the LG-BH200, the PlayStation 3, and the Samsung BD-UP5000, Profile 1.0 players can not be upgraded to be Bonus View or BD-Live compliant.

Backward compatibility

Though not compulsory, the Blu-ray Disc Association recommends that Blu-ray Disc drives should be capable of reading standard DVDs and CDs for backward compatibility.[85] A few early Blu-ray Disc players released in 2006 could play standard DVDs but not CDs.

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