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The name Blu-ray Disc is derived from the blue-violet laser used to read and write this type of disc. Because of its shorter wavelength (405 nm), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red, 650 nm laser. A single layer Blu-ray Disc can store 25 GB, over 5 times the size of a single layer DVD at 4.7GB. A dual layer Blu-ray Disc can store 50 GB, almost 6 times the size of a dual layer DVD at 8.5GB.
Blu-ray Disc is similar to PDD, another optical disc format developed by Sony (which has been available since 2004) but offering higher data transfer speeds. PDD was not intended for home video use and was aimed at business data archiving and backup.
Blu-ray Disc is currently in a "format war" with rival format HD DVD.
Technical specifications
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.
On average, a single-layer disc can hold a High Definition feature of 135 minutes using MPEG-2, with additional room for 2 hours of bonus material in standard definition quality. A dual layer disc will extend this number up to 3 hours in HD quality and 9 hours of SD bonus material.
Laser and optics
The Blu-ray Disc system uses a blue-violet 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.
Profiles
The BD-ROM specification defines four profiles of Blu-ray players. All video-based profiles are required to have a full implementation of BD-J.
1.0
This is the basic profile that all current Blu-ray players (as of April 2007) are based on. Players based on this profile are only required to have 64 KB of application data area storage, which is typically used for bookmarks and other preference storage.[citation needed] Most players have more than the minimum required 64KB.[citation needed] After October 31, 2007 this profile will be superseded by profile 1.1 as the new minimum profile.
1.1 (mandatory November 2007)
What is typically referred to as "Profile 1.1" (but is more formally known as "Final Standard Profile") adds a secondary video decoder (typically used for picture in picture), secondary audio (typically used for interactive audio and commentary) and capability of supporting a minimum of 256MB of local storage (for storing audio/video and title updates). Compliance with this profile will be mandatory for player models introduced to the market after October 31, 2007[1], but existing products will be unaffected. No players compliant with this profile have been announced or released.
Some profile 1.0 players may be upgradeable via firmware update to profile 1.1 if they have the appropriate hardware, but no manufacturer has announced any such upgrade. When software authored with interactive features dependent on Profile 1.1 hardware capabilities are played on profile 1.0 players some features may not be available or may offer limited capability. Profile 1.0 players will still be able to play the main feature of the disc, however.
2.0 (BD-Live)
Profile 2, also known as BD-Live, adds network connectivity to the list of mandatory functions and increases mandatory local storage capability to 1 GB. No players have been announced as compatible with this profile. However it has been speculated that the PS3 could be upgradeable to this profile.
3 (audio only)
Profile 3 is meant for an audio-only player and does not require video decoding or BD-J.
Hard-coating technology
Because the Blu-ray Disc standard places the data recording layer close to the surface of the disc, early discs were susceptible to contamination and scratches and had to be enclosed in plastic caddies for protection. The consortium worried that such an inconvenience would hurt Blu-ray Disc's market adoption. Blu-ray Discs now use a layer of protective material on the surface through which the data is read.
The recent introduction of a clear polymer coating has given Blu-ray Discs substantial scratch resistance. The coating is developed by TDK and is called "Durabis". It allows BDs to be cleaned safely with only a tissue. The coating is said to successfully resist "wire wool scrubbing" according to Samsung Optical technical manager Chas Kalsi. It is not clear, however, whether discs will use the Durabis coating as standard or only in premium discs.
Both Sony and Panasonic replication methods include proprietary hard-coat technologies. Sony's rewritable media are sprayed with a scratch-resistant and antistatic coating. Verbatim recordable and rewritable Blu-ray Disc discs use their own proprietary hard-coat technology called ScratchGuard
Ongoing development
Although the Blu-ray Disc specification has been finalized, engineers continue working to advance the technology. Quad-layer (100 GB) discs have been demonstrated on a drive with modified optics. Furthermore TDK announced in August 2006 that they have created a working experimental Blu-ray Disc capable of holding 200 GB of data on a single side, using six 33 GB data layers.[2] Such discs would probably not work on today's players, as these devices are only designed and tested on discs that meet the current specification.
Also behind closed doors at CES 2007, Ritek has revealed that they had successfully developed a High Definition optical disc process that extends the disc capacity of both competing formats to 10 layers. That increases the capacity of the discs to 250gb for blu-ray compared to 150gb for HD DVD using the same process. However, they noted that the major obstacle is that current reader and writer technology does not support the additional layers.[3]
JVC has developed a three layer technology that allows putting both standard-definition DVD data and HD data on a BD/DVD combo. If successfully commercialized, this would enable the consumer to purchase a disc which could be played on current DVD players, and reveal its HD version when played on a new BD player.[4] This hybrid disc does not appear to be ready for production and no titles have been announced that would utilize this disc structure.
Paper based Blu-ray Disc
On April 15, 2004, Sony Corporation and Toppan Printing, a large Japanese printing company, announced the development of the first paper-based Blu-ray Disc.[5] It functions similarly to normal Blu-ray discs, but contains 51% paper, stores up to 25GB of data, and was developed with environmental concerns in mind by using less raw material per unit of information during manufacture. Sony and Toppan said they would continue to develop the product for practical use.
BD-9
BD-9 is a red laser DVD with BD contents on. This disc should be rotated at 3X speed or more to satisfy the minimum transfer rate of 30.24Mbit/sec. No commercial production of this format is anticipated.
Codecs
Codecs are compression schemes that reduce data storage requirements; both lossy and lossless compression techniques have been developed and are being used. Depending on the application, either can be used to greatly increase the amount of audio or video storable on fixed bit-capacity media.
The BD-ROM specification mandates certain codec compatibilities for both hardware decoders (players) and the movie-software (content). For video, ISO MPEG-2, H.264/AVC, and SMPTE VC-1 are player-mandatory. (This means all BD-ROM players must be capable of decoding all three video codecs.) MPEG-2 video allows decoder backward compatibility for DVDs. H.264, sometimes called MPEG-4 part 10, is a more recent video codec. VC-1 is a competing MPEG-4 derivative codec proposed by Microsoft (based on Microsoft's previous work in Windows Media 9). BD-ROM titles with video must store video using one of the three mandatory codecs (multiple codecs on a single title are allowed).
The initial version of Sony's Blu-ray Disc-authoring software shipped with support for only 1 video-codec: MPEG-2[citation needed]. Consequently, all launch titles were encoded in MPEG-2 video[citation needed]. A subsequent update allowed the content producers to author titles in any of the 3 supported codecs: MPEG-2, VC-1, or H.264[citation needed]. 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)[citation needed]. 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 H.264) typically achieve a video runtime twice that of MPEG-2, with comparable quality.
For audio, BD-ROM players are required to support Dolby Digital AC-3, DTS, and linear PCM (up to 7.1 channels). Dolby Digital Plus, and lossless formats Dolby TrueHD and DTS HD are player optional. BD-ROM titles must use one of mandatory schemes for the primary soundtrack (linear PCM 5.1, Dolby Digital 5.1 or DTS 5.1.). A secondary audiotrack, if present, may use any of the mandatory or optional codecs.[6] For uncompressed PCM and lossless audio in Dolby TrueHD or DTS-HD Master Audio formats, Blu-ray Discs support encoding in up to 24-bit/192 kHz for a maximum of six channels, or up to eight channels with at most 24-bit/96 kHz sampling.[7]
For users recording digital television programming, the recordable Blu-ray Disc standard's datarate of 54 Mbit/s is more than adequate to record high-definition broadcasts from any source (IPTV, cable/satellite, or terrestrial.) For Blu-ray Disc movies the maximum transfer rate is 48 Mbit/s (1.5x) (both audio and video payloads together), of which a maximum of 40 Mbit/s can be dedicated to video data. This compares favorably to the maximum of 36.55 Mbit/s in HD DVD movies for audio and video data.[8]
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 will be 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 less seamless. Java creator James Gosling, at the conference, suggested that the inclusion of a Java Virtual Machine as well as network connectivity in 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 will be called BD-J and will be a subset of the Globally Executable MHP (GEM) standard. GEM is the world-wide version of the Multimedia Home Platform standard.
Region codes
The Blu-ray movie region codes are different from the DVD region codes.[9] The following are the region codes for Blu-ray discs:[10]
A/1
North America, Central America, South America, Japan, North Korea, South Korea, Taiwan, Hong Kong and Southeast Asia.
B/2
Europe, Greenland, French territories, Middle East, Africa, Australia and New Zealand.
C/3
India, Nepal, Mainland China, Russia, Central and South Asia.
Digital rights management
Blu-ray Disc has a digital rights management (DRM) feature called BD+ which allows for dynamically changing keys for the cryptographic protections involved. Should the keys currently in use be "cracked" or leaked, manufacturers can update them and build them into all subsequent discs, preventing a single key discovery from permanently breaking the entire scheme. Blu-ray Disc also mandates a Mandatory Managed Copy system, which allows users to copy content a limited number of times, but requiring registration with the content provider to acquire the keys needed; this feature was originally requested by HP.[12]
The lack of a dynamic encryption model is what made standard DVD's Content Scramble System a disaster from the industry's perspective: once CSS was cracked, all standard DVDs from then on were open to unauthorized decryption. However this controversial technology, together with Self-Protecting Digital Content (SPDC), can allow players judged "bad" to be effectively disabled,[13] preventing their use by their purchaser or subsequent owners.[14] See Advanced Access Content System (AACS).
The Blu-ray Disc Association also agreed to add a form of digital watermarking technology to the discs. Under the name "BD-ROM Mark", this technology will be built into all ROM-producing devices, and requires a specially licensed piece of hardware to insert the ROM-mark into the media during replication. All Blu-ray Disc playback devices must check for the mark. Through licensing of the special hardware element, the BDA believes that it can eliminate the possibility of mass producing BD-ROMs without authorization.
In addition, Blu-ray Disc players must follow AACS guidelines pertaining to outputs over non-encrypted interfaces. This is set by a flag called the Image Constraint Token (ICT), which would restrict the output-resolution without HDCP to 960×540. The decision to set the flag to restrict output ("down-convert") is left up to the content provider. According to CED Magazine, Sony/MGM and Disney currently have no plans to down-convert, and Fox is opposed to it as well. Warner Pictures is a proponent of the ICT, and it is expected that Paramount will also implement it.[15] Other studios releasing Blu-ray Disc content have not yet commented on whether or not they will use down-conversion. None of the titles released as of Dec 2006 include the use of the ICT. AACS guidelines require that any title that implements the ICT must clearly state so on the packaging.
Compatibility
While it is not compulsory for manufacturers, the Blu-ray Disc Association recommends that Blu-ray Disc drives should be capable of reading standard DVDs for backward compatibility. For instance, Samsung's first Blu-ray Disc drive can read CDs, regular DVDs, and Blu-ray Discs. All other Blu-ray Disc players released support DVD playback as well, however not all support CD playback. This includes Sony, Panasonic, Philips, LG, Pioneer and PC-based players from Alienware, Sony, and Dell. LG has also produced a player that is capable of playing both Blu-ray and HD DVD formats.
PC data storage
Originally, Blu-ray Disc drives in production could only transfer approximately 4.5 MB/s or 36 Mbit/s (54 Mbit/s required for BD-ROM), but 2x speed drives with a 9 MB/s or 72 Mbit/s transfer rate are now available. Rates of 8x (288 Mbit/s) or more are planned for the future. First devices used AT Attachment but newest ones support Serial ATA.
Blu-ray Disc / HD DVD comparison
The primary rival to Blu-ray Disc is HD DVD, championed by Toshiba, NEC Corporation, Microsoft, and Intel. HD DVD has a lower disc capacity per layer (15 GB vs 25 GB). However the majority of Blu-ray titles released before 2007 are in the 25 GB single layer format while almost all HD DVD movies are in the 30 GB dual layer format. [25] The first 50GB release for Blu-Ray was not made until October 2006. The Blu-ray Disc version of the Adam Sandler movie Click was released on October 10, 2006 as the first ever dual-layer release. So far in 2007 approx 30% of the new releases for Blu-ray movies were released in 25GB Discs with the other 70% being released in 50GB dual layer format. Sony's goal is to use 50 GB dual-layer discs to store up to nine hours of HD video content. Alternatively, studios releasing movies on Blu-ray Disc can choose to use VC-1 or H.264/AVC instead of MPEG-2 as an alternative way to put four hours of high-definition content on a (single layer) BD.
In terms of audio/video compression, Blu-ray Disc and HD DVD are similar on the surface: both support MPEG-2, VC-1, and H.264 for video compression, and Dolby Digital (AC-3), PCM, and DTS for audio compression. The first generation of Blu-ray Disc movies released used MPEG-2 (the standard currently used in DVDs, although encoded at a much higher video resolution and a much higher bit rate than those used on conventional DVDs), while initial HD DVDs releases used the VC-1 codec. Due to greater total disc capacity, the Blu-ray Disc producers may choose in the future to utilize a higher maximum video bit rate, as well as potentially higher average bit rates. In terms of audio, there are some differences. Blu-ray Disc allows conventional AC-3 audiotracks at 640 kbit/s, which is higher than HD DVD's maximum of 504 kbit/s. Nevertheless, Dolby Digital Plus support is mandatory for standalone HD DVD players at a maximum of 3 Mbit/s, while optional for BD players with support at a bitrate of 1.736 Mbit/s.[26]
Both HD DVD and Blu-ray Disc support the 24p (traditional movie) frame rate, but technical implementations of this mode are different between the formats. Blu-ray Disc supports 24p with its native timing, while HD DVD uses 60i timing for 24p (encoded progressively, replacing missing fields with "repeat field flags"). Decoders can ignore the “flags” to output 24p.[27] There is no impact on picture resolution or storage space as a result of this, as the HD DVD format uses the same video information—it simply adds notational overhead.
Currently, five Hollywood studios exclusively support Blu-ray Disc: Columbia Pictures, MGM, Disney, Lionsgate and 20th Century Fox (Columbia Pictures and MGM are owned by Sony Pictures). Four Hollywood studios support both Blu-ray and HD DVD: Paramount Pictures, DreamWorks, Warner Bros. and New Line Cinema (the former two are owned by Viacom, and the latter two by Time Warner). Two Hollywood studios exclusively support HD DVD: Universal Studios and the Weinstein Company.
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