| A Blu-ray Disc (also called BD) is a high-density optical | | | | continue to develop the product for practical use. |
| disc format for the storage of digital media, including | | | | Software standards |
| high-definition video. | | | | Codecs |
| Overview | | | | Codecs are compression schemes that can be used |
| The name Blu-ray Disc is derived from the blue-violet | | | | to store audio and video information on a disc. The |
| laser used to read and write this type of disc. Because | | | | BD-ROM specification places requirements on both |
| of this shorter wavelength (405 nm), substantially more | | | | hardware decoders (players) and the movie-software |
| data can be stored on a Blu-ray Disc than on the | | | | (content). |
| common DVD format, which uses a red, 650 nm laser. | | | | For video, ISO MPEG-2, H.264/AVC, and SMPTE |
| Blu-ray Disc can store 25 GB on each layer, as | | | | VC-1 are player-mandatory. (This means all BD-ROM |
| opposed to a DVD's 4.7 GB. Several manufacturers | | | | players must be capable of decoding all three video |
| have released single layer and dual layer (50 GB) | | | | codecs.) MPEG-2 video allows decoder backward |
| recordable BDs and rewritable discs.[1] All supporting | | | | compatibility for DVDs. H.264, sometimes called |
| studios have either already released or have | | | | MPEG-4 part 10, is a more recent video codec. VC-1 is |
| announced release of movies on 50GB discs. | | | | a competing MPEG-4 derivative codec proposed by |
| Blu-ray Disc is similar to PDD, another optical disc | | | | Microsoft (based on Microsoft's previous work in |
| format developed by Sony (which has been available | | | | Windows Media 9). BD-ROM titles with video must |
| since 2004) but offering higher data transfer speeds. | | | | store video using one of the three mandatory codecs |
| PDD was not intended for home video use and was | | | | (multiple codecs on a single title are allowed). |
| aimed at business data archiving and backup. Blu-ray | | | | Initial versions of Sony's Blu-ray Disc-authoring |
| Disc is currently in a format war with rival format HD | | | | software only included support for MPEG-2 video, so |
| DVD. | | | | the initial Blu-ray Discs were forced to use MPEG-2 |
| Technical Specifications | | | | rather than the newer codecs, VC-1 and H.264. An |
| About 9 hours of high-definition (HD) video can be | | | | upgrade was subsequently released supporting the |
| stored on a 50 GB disc. | | | | newer compression methods so the second wave of |
| About 23 hours of standard-definition (SD) video can | | | | Blu-ray Disc titles were able to make use of this. The |
| be stored on a 50 GB disc. | | | | choice of codecs affects disc cost (due to related |
| On average, a single-layer disc can hold a High | | | | licensing/royalty payments) as well as program |
| Definition feature of 135 minutes using MPEG-2, with | | | | capacity. The two more advanced video codecs can |
| additional room for 2 hours of bonus material in | | | | typically achieve twice the video runtime of MPEG-2. |
| standard definition quality. A dual layer disc will extend | | | | When using MPEG-2, quality considerations would limit |
| this number up to 3 hours in HD quality and 9 hours of | | | | the publisher to around two hours of high-definition |
| SD bonus material. | | | | content on a single-layer (25 GB) BD-ROM. |
| Laser and optics | | | | For audio, BD-ROM players are required to support |
| The Blu-ray Disc system uses a blue-violet laser | | | | Dolby Digital AC-3, DTS, and linear PCM (up to 7.1 |
| operating at a wavelength of 405 nm, similar to the | | | | channels). Dolby Digital Plus, and lossless formats Dolby |
| one used for HD DVD, to read and write data. | | | | TrueHD and DTS HD are player optional. BD-ROM |
| Conventional DVDs and CDs use red and infrared | | | | titles must use one of mandatory audiotracks for the |
| lasers at 650 nm and 780 nm respectively. | | | | primary soundtrack (linear PCM 5.1, Dolby Digital 5.1 or |
| Hard-coating technology | | | | DTS 5.1.). A secondary audiotrack, if present, may use |
| Because the Blu-ray Disc standard places the data | | | | any of the mandatory or optional codecs.[8] For |
| recording layer close to the surface of the disc, early | | | | uncompressed PCM and lossless audio in Dolby |
| discs were susceptible to contamination and scratches | | | | TrueHD or DTS-HD Master Audio formats, Blu-ray |
| and had to be enclosed in plastic caddies for | | | | Discs support encoding in up to 24-bit/192 kHz for up |
| protection. The consortium worried that such an | | | | to six channels, or up to eight channels of up to 24-bit |
| inconvenience would hurt Blu-ray Disc's market | | | | 96 kHz encoding.[9] For reference, even new |
| adoption. Blu-ray Discs now use a layer of protective | | | | big-budget Hollywood films are mastered in only 24-bit |
| material on the surface through which the data is read. | | | | 48 kHz, with 16-bit/48 kHz being common for ordinary |
| Both Sony and Panasonic replication methods include | | | | films. |
| proprietary hard-coat technologies. Sony's rewritable | | | | For users recording digital television broadcasts, the |
| media are sprayed with a scratch-resistant and | | | | Blu-ray Disc's baseline datarate of 54 Mbit/s is more |
| antistatic coating. | | | | than adequate to record high-definition broadcasts. |
| TDK also announced a way to remedy the problem in | | | | Support for new codecs will evolve as they are |
| January 2004 with the introduction of a clear polymer | | | | encapsulated by broadcasters into their MPEG-2 |
| coating that gives Blu-ray Discs substantial scratch | | | | transport streams, and consumer set-top boxes |
| resistance. The coating was developed by TDK and is | | | | capable of decoding them are rolled out. For Blu-ray |
| called "Durabis". It allows BDs to be cleaned safely with | | | | Disc movies the maximum transfer rate is 54 Mbit/s |
| only a tissue. The coating is said to successfully resist | | | | (1.5x) for the combined audio and video payload, of |
| "wire wool scrubbing" according to Samsung Optical | | | | which a maximum of 40 Mbit/s can be dedicated to |
| technical manager Chas Kalsi. It is not clear, however, | | | | video data. This compares favorably to the maximum |
| whether discs will use the Durabis coating or if the use | | | | of 36.55 Mbit/s in HD DVD movies for audio and video |
| of the coating will prove too expensive. | | | | data.[10] |
| Since the claims of Chas Kalsi, several videos have | | | | Java software support |
| appeared on YouTube of people testing these claims, | | | | At the 2005 JavaOne trade show, it was announced |
| usually on copies of Talladega Nights included as | | | | that Sun Microsystems' Java cross-platform software |
| freebies with some PS3 units. The results seem to | | | | environment would be included in all Blu-ray Disc |
| support Kalsi entirely with the disc undergoing | | | | players as a mandatory part of the standard. Java will |
| extensive steel wool scrubbing and vicious attacks | | | | be used to implement interactive menus on Blu-ray |
| with pens and pizza cutters and still achieving normal | | | | Discs, as opposed to the method used on DVD video |
| playback on the PS3 console. | | | | discs, which uses pre-rendered MPEG segments and |
| Verbatim announced in July 2006 that their Blu-ray | | | | selectable subtitle pictures, which is considerably more |
| Disc recordable and rewritable discs would incorporate | | | | primitive and less seamless. Java creator James |
| their hard-coat ScratchGuard technology which | | | | Gosling, at the conference, suggested that the inclusion |
| protects against scratches, abrasion, fingerprints, and | | | | of a Java virtual machine as well as network |
| traces of grease.[4][5] | | | | connectivity in BD devices will allow updates to Blu-ray |
| Ongoing development | | | | Discs via the Internet, adding content such as additional |
| Although the Blu-ray Disc specification has been | | | | subtitle languages and promotional features that are |
| finalized, engineers continue working to advance the | | | | not included on the disc at pressing time. This Java |
| technology. Quad-layer (100 GB) discs have been | | | | Version will be called BD-J and will be a subset of the |
| demonstrated. And TDK announced in August 2006 | | | | Globally Executable MHP (GEM) standard. GEM is the |
| that they have created a working experimental Blu-ray | | | | world-wide version of the Multimedia Home Platform |
| Disc capable of holding 200 GB of data on a single | | | | standard. |
| side, using six 33 GB data layers.[6] Such discs would | | | | The BD-ROM specification defines four profiles of |
| almost certainly not work on some of today's Blu-ray | | | | Blu-ray players. All video-based profiles are required to |
| Disc players, as these devices are only designed and | | | | have a full implementation of BD-J. The 1st generation |
| tested on discs that meet the current specification. | | | | players are based on the Profile 1 (BD-Video) |
| Paper based Blu-ray Disc | | | | specification that does not require support of certain |
| On April 15th 2004, Sony Corporation and Toppan | | | | features such as Picture-in-Picture, secondary audio, |
| Printing, a large Japanese printing company, announced | | | | local storage, and network connections. Profile 1.1 |
| the development of the first paper-based Blu-ray | | | | makes PIP, secondary audio and local storage |
| Disc.[7] Compared to normal Blu-ray discs it contained | | | | mandatory. Profile 2 (BD-Live) adds network |
| 51% paper, could store 25GB of data, and was | | | | connectivity to the list of mandatory functions. Profile 3 |
| developed with environmental concerns in mind as it | | | | is meant for an audio-only player and does not require |
| used less raw material usage per unit of information | | | | video decoding or BD-J. |
| during manufacture. Sony and Toppan said they would | | | | |