CD History
Short for CD according to abbreviationfinder, the compact disc was created by the Dutch Kees Immink of Philips and the Japanese Toshitada Doi of Sony in 1979. The following year, Sony and Philips, which had developed the Compact Disc digital audio system, began distributing compact discs, but sales were unsuccessful due to the economic slump at the time. So they decided to embrace the higher quality classical music market. The launch of the new and revolutionary audio recording format began, which would later be extended to other sectors of data recording. The optical system was developed by Philips while Digital Reading and Coding was carried out by Sony, it was presented in June 1980 to the industry and 40 companies from all over the world joined the new product by obtaining the corresponding licenses for the production of players and discs.
In 1981, the conductor Herbert von Karajan, convinced of the value of compact discs, promoted them during the Salzburg festival and from that moment his success began. The first titles recorded on compact discs in Europe were Richard Strauss’s Alpine Symphony, Frédéric Chopin’s waltzes performed by Chilean pianist Claudio Arrau and ABBA’s The Visitors album, in 1983 the first compact disc would be produced in the United States by CBS (Today Sony Music) being the first title on the market a Billy Joel album. The production of compact discs was centralized for several years in the United States and Germany from where they were distributed throughout the world, and in the nineties factories were installed in various countries. For example, in 1992 Sonopress produced in Mexico the first CD titled “De Mil Colores” by Daniela Romo.
In 1984, CDs entered the world of computing, allowing storage of up to 700 MB. The diameter of the central perforation of the compact discs was determined in 15 mm, when between meals, the creators were inspired by the diameter of the 10 cent guilder from Holland. In contrast, the diameter of compact discs is 12 cm, which corresponds to the width of the top pockets of men’s shirts, because according to Sony’s philosophy, everything had to fit there.
Standards
There are numerous standards that describe how information should be stored on a compact disc based on its intended use. These standards are referenced in documents called books and each one has an assigned color:
- Red Book (also known as Red Book Audio) – It was developed in 1980 by Sony and Philips and describes the physical format of a CD and the encoding method for an Audio CD (sometimes referred to as CD-DA, Compact Disc – Digital audio). Sets a sample rate of 44.1 kHz and 16-bit resolution (in stereo) for recording audio data.
- Yellow Book: developed in 1984 to describe the physical format of data CDs (CD-ROM, Compact Disc – Read-only memory). It includes two modes:
- CD-ROM Mode 1, used to store data with error correction (ECC, Error Correction Code) and to avoid data loss due to disk degradation.
- CD-ROM Mode 2, used to store compressed graphics, video and audio data. To be able to read this type of CD-ROM, a drive must support Mode 2.
- Green book: the physical specifications for a CD-I (Philips Interactive CD).
- Orange book: physical format for recordable CDs. It is divided into three sections:
- Part I: the CD-MO format (magneto-optical discs)
- Part II: the CD-WO format (write-only discs, currently called CD-R)
- Part III: the CD-RW (CD Rewritable) format
- White paper: physical format for Video CD (VCD).
- Blue Book: physical format for “Extra” CDs (CD-XA)
Logical structure
The Orange Book establishes that a CD-R, be it an audio CD or a CD-ROM, is made up of three areas that make up the information area:
- The input area (sometimes called LIA) contains only information that describes the contents of the disc in the table of contents (TOC). The entry zone extends from a radius of 23 mm starting from the edge to a radius of 25 mm. This size becomes mandatory due to the need to store information in a maximum of approximately 99 tracks. The input zone allows the CD player / drive to follow the spiral holes to synchronize with the data located in the program zone.
- The Program Zone is the section of the disc that contains the data. It starts 25mm from the center, extending to a 58mm radius. It can contain the equivalent of 76 minutes of audio data. The program area can in turn contain up to 99 tracks (or sessions), each with a minimum length of 4 seconds.
- The Out Zone (or LOA) contains no data (silence on an audio CD) and marks the end of a CD. It starts at a 58mm radius and must be at least 0.5mm wide (radius). The exit zone must, in this way, contain at least 6750 sectors or 90 seconds of silence at minimum speed (1x).
In addition to the areas described above, a CD-R contains a PCA (Power Calibration Area) and a PMA (Program Memory Area). Together they constitute the SUA (System User Area). The PCA can be interpreted as a test area for the laser, so that its power can be calibrated according to the type of disk being read. This area allows blank CDs to be sold, which in turn use different tints and layers of reflection. Each time it is reset, the recorder recognizes that it has performed a test. In this way, up to 99 tests per disk are allowed.
File System
The format of the CD (or more precisely the file system) describes the way the data is stored in the program area.
The first file system for CDs was the High Sierra Standard.
The ISO 9660 format, standardized in 1984 by the ISO (International Standards Organization), takes up the High Sierra Standard to define the structure of files and folders on CD-ROMs. It is divided into three levels:
- Level 1: A formatted ISO 9660 Level 1 CD-ROM can only contain files with names that contain only uppercase letters (AZ), digits (0-9), and the “_” character. Together these characters are called d characters. Folder names can contain a maximum of 8 characters d and cannot be more than 8 subfolders deep. In addition, the ISO 9660 standard requires that each file be stored on the CD-ROM continuously, without fragmentation. This is the most restrictive level. Compliance with level 1 ensures that the disc will be readable on a large number of platforms.
- Level 2: The ISO 9660 level 2 format requires each file to be stored as a continuous stream of bytes, but is instead more flexible with file names and allows the characters @ – ^! $% & () # ~ and a depth of up to 32 subfolders.
- Level 3: The ISO 9660 Level 3 format does not restrict file and folder names.
Microsoft also created the Joliet format, an expansion of ISO 9660 that allows you to use long file names (LFNs) of up to 64 characters, including spaces and accented characters according to Unicode encoding.)
The ISO 9660 Romeo format is a nomenclature option proposed by Adaptec, therefore independent from the Joliet format. It allows you to store files whose names can be up to 128 characters long, but it does not support Unicode encoding.
The ISO 9660 RockRidge format is an extension of the ISO 9660 nominalization that makes it compatible with UNIX file systems.
In order to compensate for the limitations of ISO 9660 (which make it unsuitable for DVD-ROM discs), the Optical Storage Technology Association (OSTA has developed the ISO 13346 format, known as UDF (Universal Disc Format).
Writing methods
- Monosession: This method creates a single session on disk and does not allow new data to be added later.
- Multisession: Unlike the previous method, this allows the CD to be written multiple times, creating a 14MB table of contents (TOC) for each of the sessions.
- Multivolume: It is the multisession type recording that considers each session as a different volume.
- Track At Once: This method allows you to disable the laser between two tracks, thus creating a two-second pause between each track on an audio CD.
- Disc At Once: Unlike the previous method, this method writes the entire CD at once (without pauses).
- Packet writing: This method allows you to write the data in packets.
Technical specifications
A CD-ROM drive is defined as follows:
- Speed – Speed is calculated relative to the speed of an audio CD player (150 KB / s). A drive that can reach speeds of 3000 KB / s will be considered 20x (20 times faster than a 1x drive).
- Access time: represents the average time to go from one part of the CD to another.
- Interface: ATAPI (IDE) or SCSI
