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Blu Ray Technology

Blu Ray Technology

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Thursday, 05 July 2007
A Blu-ray Disc (also called BD) is a high-density optical disc format for the storage of digital media, including high-definition video. 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 4.7 GB. A dual layer Blu-ray Disc can store 50 GB, almost 6 times the size of a dual layer DVD at 8.5 GB. 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. 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. Most players have more than the minimum required 64 KB. 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 256 MB 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, 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. Players of earlier profiles will still be able to play the main feature of the disc, however. 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 a 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. 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 250 GB for Blu-ray compared to 150 GB 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. 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 30.24 Mbit/s. No commercial production of this format is anticipated. Software standards 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 initial version of Sony's Blu-ray Disc-authoring software shipped with support for only 1 video-codec: MPEG-2. Consequently, all launch titles were encoded in MPEG-2 video. A subsequent update allowed the content producers to author titles in any of the 3 supported codecs: MPEG-2, VC-1, or H.264. 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, Dolby Digital, or DTS). A secondary audiotrack, if present, may use any of the mandatory or optional codecs. 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. 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. Applications 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. Stand-alone players The home video game console system PlayStation 3 (Sony) is shipped with a 2x Blu-ray Disc drive. The drive is read-only as is the case with most game console optical drives. According to Sony's press releases, it supports DVD (8x), CD (24x), and SACD (2x) formats in addition to BD-ROM, BD-R, and BD-RE. Full HD 1080/60p and 24p True Cinema Video Output. AVCHD Media playback with x.v.Color output. On January 4, 2006, at the Consumer Electronics Show Philips announced their first Blu-ray Disc consumer product to the U.S. market. On April 13, 2006, Panasonic announced its first Blu-ray Disc player for the U.S. market, the DMP-BD10 would be shipping together in late 2006 along with their first commercially available plasma 1080p HDTVs. Blu-ray Disc / HD DVD comparison HD DVD has a lower disc capacity per layer (15 GB vs 25 GB). However the vast 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. 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. Blu-ray also supports Dolby TrueHD, lossless encoding of up to 8 channels of audio, DTS-HD High Resolution Audio and DTS-HD Master Audio, a lossless encoding of up to 8 channels of audio. 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. 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. The Blu-ray / HD DVD "format war" Blu-ray Disc is currently in a "format war" with rival format HD DVD, to determine which (if any) of the two formats will become the leading carrier for high-definition content to consumers From Wikipedia, the free encyclopedia Copyright (C) 2000,2001,2002 Free Software Foundation, Inc. Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
Last Updated ( Friday, 20 July 2007 )

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