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| Orange Book CD-r standard technical specification |
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The CD-R, originally named CD Write-Once (WO), specification was first published in 1988 by Philips and Sony in the 'Orange Book'. The Orange Book standard consists of several parts, furnishing details of the CD-WO, CD-MO (Magneto-Optic), and CD-RW (ReWritable). For Orange book CD Replication Prices see >> The latest editions have abandoned the use of the term "CD-WO" in favor of "CD-R", while "CD-MO" were practically never used. Written CD-Rs and CD-RWs are fully compatible with the Audio CD (Red Book) and CD-ROM (Yellow Book) standards. They use Eight-to-Fourteen Modulation, CIRC error correction plus the third error correction layer defined for CD-ROM. The dye materials developed by Taiyo Yuden made it possible for CD-R discs to be compatible with Audio CD and CD-ROM discs. A standard CD-R is a 1.2 mm thick disc made of polycarbonate with a 120 mm or 80 mm diameter. CD-r has a storage capacity of 74 minutes of audio or 650 MiB of data. CD-R/RWs are also available with capacities of 79 minutes, 59 seconds and 74 frames (marketed as 80 minutes) /736,966,656 bytes (702 MiB), which they achieve by burning at the maximum allowable tolerances specified in the Orange Book CD-R/CD-RW standards. Most CD-Rs on the market have an 80 minute capacity. There are also 90 minute/790 MiB and 99 minute/870 MiB discs, although they are rare. Some drives use special techniques to write more data onto a given disc, such as Plextor's GigaRec allowing as much as 1.2 GiB onto a 99 minute disc. Also, due to the limitations of the data structures in the ATIP (see below), 90 and 99 minute blanks will identify as 80 minute ones and have to be burned using the "overburn" options in the CD recording software. The polycarbonate disc contains a spiral groove to guide the laser beam upon writing and reading information. The disc is coated on the side with the spiral groove with a very thin layer of organic dye and subsequently with a thin, reflecting layer of silver, a silver alloy or gold. Finally, a protective coating of a photo-polymerizable lacquer is applied on top of the metal reflector and cured with UV-light. The blank disc has a pre-groove track onto which the data is written. The pre-groove track, which also contains timing information, ensures that the recorder follows the same spiral path as a conventional CD. A CD recorder writes data to a CD-R disc by pulsing its laser to heat areas of the organic dye layer. The writing process does not produce indentations (pits); instead, the heat permanently changes the optical properties of the dye, changing the reflectivity of those areas. Using a low laser power, so as not to further alter the dye, the disc is read back in the same way as a CD-ROM. However, the reflected light is modulated not by pits, but by the alternating regions of heated and unaltered dye. The change of the intensity of the reflected laser radiation is transformed into an electrical signal, from which the digital information is recovered ("decoded"). Once a section of a CD-R is written, it cannot be erased or rewritten, unlike a CD-RW. A CD-R can be recorded in multiple sessions. A CD recorder can write to a CD-R using several methods including: Disc At Once - the whole CD-R is written in one session with no gaps and the disc is "closed" meaning no more data can be added and the CD-R effectively becomes a standard read-only CD. With no gaps between the tracks the Disc At Once format is useful for "live" audio recordings. Track At Once - data is written to the CD-R one track at a time but the CD is left "open" for further recording at a later stage. It also allows data and audio to reside on the same CD-R. Packet Writing - used to record data to a CD-R in packets allowing extra information to be appended to a disc at a later time or information on the disc can be made "invisible". In this way CD-R can emulate CD-RW however each time information on the disc is altered more data has to be written to the disc. There can be compatibility issues with this format and some CD drives. A rough estimation of the amount of data on a CD-R can be gained by inspecting the playback side of the disc. A visible variation in the surface can be observed. CD-Rs are written from the center of the disc outwards. See Also Red Book Audio CD Standard Yellow Book CD Standard White CD Standard Blue Book Enhanced CD, CD+G and CD-Plus Orange Book CD Standard CD-r CD-RW |
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