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| Media type | Optical disc |
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| Encoding | Various |
| Capacity | Typically up to 700 MB (up to 80 minutes audio) |
| Read mechanism | 600–780 nm wavelength (infrared and red edge) semiconductor laser, 1,200 kbit/s (1×) to 100 Mb/s (56×) |
| Write mechanism | 780 nm wavelength (infrared and red edge) semiconductor laser |
| Standard | Rainbow Books |
| Developed by | Philips, Sony |
| Usage | Audio and data storage |
| Extended from | Recordable LaserDisc CD-ROM |
| Extended to | CD-RW DVD-R |
| Released | 1988;38 years ago (1988) |
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Optical media types
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Standards
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In the United States, there is a market separation between "music" CD-Rs and "data" CD-Rs, the former being notably more expensive than the latter due to industry copyright arrangements with the RIAA. Specifically, the price of every music CD-R includes a mandatory royalty disbursed to RIAA members by the disc manufacturer; this grants the disc an "application flag" indicating that the royalty has been paid. Consumer standalone music recorders refuse to burn CD-Rs that are missing this flag. Professional CD recorders are not subject to this restriction and can record music to discs with or without the flag. The two types of discs are functionally and physically identical other than this, and computer CD burners can record data and/or music to either. New music CD-Rs are still being manufactured as of the late 2010s, although demand for them has declined as CD-based music recorders have been supplanted by other devices incorporating the same or similar functionality. The groove on the surface of a CD-R disc is not a perfect spiral and contains slight sinusoidal deviations called wobble. Frequency modulation is used to encode data into the wobble with a carrier frequency of 22.05 kHz. This method of storing information is called Absolute Time in Pregroove (ATIP). Within the ATIP data is a 7-bit field called Disc Application Code containing bits U1 through U7. The first bit, U1, is used to determine if a CD-R is considered a "music" CD-R. U1 bit valuesedit
Physical characteristicseditThere are many hybrid variations of the dye formulations, such as Formazan by Kodak (a hybrid of cyanine and phthalocyanine). Many manufacturers have added additional coloring to disguise their unstable cyanine CD-Rs in the past, so the formulation of a disc cannot be determined based purely on its color. Similarly, a gold reflective layer does not guarantee the use of phthalocyanine dye. The quality of the disc is also not only dependent on the dye used, it is also influenced by sealing, the top layer, the reflective layer, and the polycarbonate. Simply choosing a disc based on its dye type may be problematic. Furthermore, correct power calibration of the laser in the writer, as well as correct timing of the laser pulses, stable disc speed, and so on, is critical to not only the immediate readability but the longevity of the recorded disc, so for archiving it is important to have not only a high-quality disc but a high-quality writer. In fact, a high-quality writer may produce adequate results with medium-quality media, but high-quality media cannot compensate for a mediocre writer, and discs written by such a writer cannot achieve their maximum potential archival lifetime. Speededit
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