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