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