Red Book (audio CD standard)
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| Media type | Optical disc |
|---|---|
| Encoding | 2 channels of PCM audio, each signed 16-bit values sampled at 44100 Hz |
| Capacity | up to 700 MB |
| Read mechanism | 780 nm wavelength semiconductor laser |
| Developed by | Sony & Philips |
| Usage | Audio and data storage |
Red Book is the standard for audio CDs (Compact Disc Digital Audio system, or CDDA). It is named after one of a set of color-bound books that contain the technical specifications for all CD and CD-ROM formats.
The first edition of the Red Book was released in 1980 by Philips and Sony;[1] it was adopted by the Digital Audio Disc Committee and ratified as IEC 60908. The standard is not freely available and must be licensed from Philips. As of 2004, the cost per the relevant Philips order form [2] is US$5,000. As of 2006, the IEC 60908 document is also available as a PDF download for $242.[3]
Contents |
[edit] Red Book Audio Specifications
The basic specifications state that
- Maximum playing time is 74 minutes (including pauses)
- Minimum duration for a track is 2 seconds
- Maximum number of tracks is 99
- Maximum number of index points (subdivisions of a track) is 99 with no maximum time limit
- International Standard Recording Code (ISRC) should be included
[edit] Technical details
The Red Book specifies the physical parameters and properties of the CD, the optical "stylus" parameters, deviations and error rate, modulation system (eight-to-fourteen modulation, EFM) and error correction (cross-interleaved Reed-Solomon coding, CIRC), and subcode channels and graphics.
It also specifies the form of digital audio encoding: 2-channel signed 16-bit PCM sampled at 44,100 Hz. This sample rate is adapted from that attained when recording digital audio on PAL videotape with a PCM adaptor, an earlier way of storing digital audio.
An audio CD can represent frequencies up to 22.05 kHz, the Nyquist frequency of the 44.1 kHz sample rate.
The bit rate is 1411.2 kbit/s:
2 channels x 44,100 samples per second per channel × 16 bits per sample = 1,411,200 bit/s = 1,411.2 kbit/s.
As each sample is a signed 16-bit two's complement integer, sample values range from -32768 to +32767.
On the disc, the data is stored in sectors of 2352 bytes each, read at 75 sectors per second. Onto this the overhead of EFM, CIRC, L2 ECC, and so on, is added, but these are not typically exposed to the application reading the disc.
By comparison, the bit rate of a "1x" data CD is defined as 2048 bytes per sector × 75 sectors per second = 150 KiB/s, or approximately 9.2 million bytes per minute.
[edit] Copy protection
Some major recording publishers have begun to sell CDs that violate the Red Book standard. Some do so for the purpose of copy protection, using systems like Copy Control.
Some do so for extra features such as DualDisc, which includes both a CD layer and a DVD layer whereby the CD layer is much thinner, 0.9 mm, than required by the Red Book, which stipulates a nominal 1.2 mm, but at least 1.1 mm. Philips and many other companies have warned them that including the Compact Disc Digital Audio logo on such non-conforming discs may constitute trademark infringement. Either in anticipation or in response, recent copy-protected CDs bear stickers and warnings that the CD is not standard and may not play in all CD players, and no longer display the long-familiar logo.
[edit] See also
- Extended Copy Protection—source of the Sony DRM scandal
- DRM (computing)
- Four-channel compact disc digital audio
[edit] External links
[edit] References
- ^ "How the CD was developed". BBC News. August 17, 2007. http://news.bbc.co.uk/2/hi/technology/6950933.stm. Retrieved on 2007-08-17.
- ^ Document no. 28/10/04-3122 783 0027 2
- ^ IEC 60908 Ed. 2.0 b:1999 Audio recording - Compact disc digital audio system
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