CD/DVD INFORMATION

History of CD/DVD

The first disc that could be written and read by optical means (using light as a medium) was developed by James T. Russell. In the late 1960s, Russell created a system that recorded, stored, and played audio/video data using light rather than the traditional contact methods, which could easily damage the disks during playback. Russell developed a photosensitive disc that stored data as 1 micron-wide dots of light and dark. The dots were read by a laser, converted to an electrical signal, and then to audio or visual display for playback.

Russell's own company manufactured the first disc player in 1980, although the technology never reached the marketplace until Philips and Sony developed the technology. In late 1982, Philips and Sony released the first of the compact disc (CD) formats, which they then called CD-DA (digital audio). In the years since, format has followed format as the original companies and other industry members developed more adaptations of the original specifications.

Digital Versatile disc (DVD) had its beginning in 1994, when two formats, Super disc (SD) and Multimedia CD (MMCD) were introduced. Promoters of the competing technologies failed to reach an agreement on a single standard until 1996, when DVD was selected as a convergence format. DVD has, in the few years since, grown to include variations that do anything that CD does, and more efficiently. Standardization and compatibility issues aside, DVD is well-placed to supplant CD. 

Development of the Compact Disc, CD-ROM, DVD and Blu-Ray

1841: French mathematician Augustin-Louis Cauchy proposed Sampling Theorem, which was used in the conversion of audio into digital format.
1842: An analytical engine for storing and performing calculations developed by Charles Babbage, a British mathematician and inventor.
1854: George Boole, a British mathematician, published theoretical concept used in digital circuits.
1855: Phono-autograph, a device used to record vibrations on a carbonized paper, was invented by Leon Scott de Martinville, a French printer-turned-inventor.
1877: Thomas Edison, an American inventor and scientist, invented the phonograph, an earlier version of the gramophone.
1887: Edison’s Wax Cylinder Phonograph replaced by the first ever audio disc, which was invented by American Emile Berliner.
1915: First 10-inch 78 rpm gramophone record introduced.
1922: The concept of time sampling in communication introduced by John Renshaw Carson.
1928: Technology used for today’s audio CDs proposed and proved in theory by Harry Nyquist, a Swedish physicist.
1937: Alec Reeves, a British scientist, invented pulse-code modulation technology, which is still being used in audio CDs today.
1947: Magnetic tape recorders introduced in US markets.
1948: Claude Shannon, American mathematician and “Father of Information Theory”, published Mathematical Theory of Communication, which contributed significantly to CD technology.
1949: 7-inch 45 rpm records introduced in the US markets.
1950: Richard Hamming, an American mathematician, published Theory of Error Detection and Corrections, an important document for the manufacturing of error-free CDs.
1958: Jack Kilby at Texas Instruments introduced the integrated circuit.
1960: Laser technology introduced by Theodore Maiman and used for data storage in CDs. Irving Stoy Reed and Gustave Soloman invented the Reed Solomon code, an algebraic error-correcting and detection code, which was used for reading and encoding CDs.
1965: James Russell, an American inventor, introduced the concept of optical digital recording and playback.
1967: 12-bit PCM digital audio recording demonstrated at NHK Technical Research Institute, Japan. The audio was recorded onto a high grade video tape.
1969: The idea of a compact disc was born in the mind of Klass Compaan, a Ducth physicist.
1970: A glass disc prototype that was readable by laser was created by Klass Compaan and Pete Kramer at Philips.
1971: Intel produced the microprocessor.
1972: First color prototype of the compact disc produced by Kramer and Compaan.
1975: Research on laser and optical disc technology started by Sony.
1977: Philips began researching laser and optical disc technology.
1976: Demonstration of an optical digital audio disc by Sony.
1978: Sony demonstrated an advanced version of optical digital audio disc with playing time of 150 minutes.
1979: Philips launched compact disc.
1980: CD-DA format introduced by Philips and Sony, and standards were laid down in the Red Book.
1981: First test CD created in Hannover, Germany by the Polydor Pressing Operations plant.
1982: Manufacturing of CDs began on a large scale in a factory.
1982: First ever album on a CD released by Sony, which was Billy Joel’s 52nd Street.
1983: CD players and discs hit the market in the US and the rest of the world.
1984: Advanced technology to store and retrieve data from CD-ROM introduced.
1985: CD-ROM drives introduced in the US and world markets. Dire Straits became the first artist to sell a million copies on CD.
1986: CD-I, the interactive CD concept, was introduced.
1987: The first Video CD (VCD) format created for storing and playing video and audio.
1988: The concept of CD-R, a recordable CD, was born.
1990: Philips and Sony created a recordable CD called the CD-R.
1991: CD-I format created and launched in the market.
1996: DVD technology hit the world, through the collaboration of leading computer companies such as Sun, Apple, Dell, and many more.
1997: DVD released in the market, sidelining CDs. Rewritable CDs and CD-RW introduced in the market.
1999: Super Audio CD is released by Sony and Philips as a higher quality digital audio recording.
2000: DVD-Audio is released as a competitor to Super Audio CDs, neither of which achieved much success on the mass market.
2000: The DVR Blue prototypes are unveiled, later to become known as Blu-Ray discs.
2003: The first consumer available Blu-Ray player is released in Japan by Sony.
2008: Sales for large label CDs drops 20% due to rising popularity of MP3 audio.

Optical track
Optical track is a recording unit of data on the disc. The information stored on CD-ROM is arranged according to certain rules, and is shaped like an "Optical track", called "light rail" in spiral shapes. The data from the directory inside the CD-ROM (TOC, Table of Contents) is recorded in the starting address of the number of consecutive logical sectors of an Optical track. The audio CD in a song is corresponding to a light rail, therefore, there are many light rails. CD-ROM light rails are at most 99 in number.

The minimum length of Optical tracks
The minimum length of each light rail is indicated by Time: 4 seconds, or 300 sectors.
This value is sometimes referred to as "threshold." Less than 4 seconds, light rail, if it can not be used as light rail, it might be a "bad Optical track"

Pit and land
The depression part on the Optical track is called information pit and the flat part is called land. Pit and land are used to record information.



CD-R disc has been pressed with spiral groove, known as the "pre-groove", instead the pit of optical track. When burning, CD-R disc in a trench in an organic dye laser irradiation, the formation of bubbles, this is the "pit". Bubbles, once formed, will not be able to restore the status quo, therefore, CD-R can only be written once.

EFM (Eight-to-Fourteen Modulation)
These "pit" and "land" is the signal after "8-14 coded modulation" (EFM, Eight to Fourteen Modulation), plus three interval code could access code to form inside the burning to disc. This treatment can guarantee the accuracy of reading the signal.



When the laser head of CD-ROM drive reads the data, the "pit" and "land" reflection coefficient is not the same, but they are read as "0" and only the "pit", "land" conversions is read as "1". The length of Pit" and "land" decides the number of"0". 8-bit data have two or more of the "1", CD-ROM accesses can not be achieved. To this end, two consecutive "1" between the use of at least two "0", up to 10 "0" separated them. EFM is to extract the 14-bit data and 256 does not appear for two consecutive "1" of data (access code) and the 8-bit data correspond. In order to avoid the adjacent two data channels being two yards, "one" and therefore the channel between the plus three yards combined yards (DVD using two combined yards), the formation of 17-channel code. This channel code can be used directly for burning CDs. Reading the disc, it will be 17 yards through the channel decoding system to be converted to 8-bit binary data.

The capacity of CD
The amount of data stored in the disc is the capacity of CD. It is usually measured in MB. A standard CD-R disc is used to record data, its capacity is 650MB. But now they have large capacity, for example, 700MB.
The capacity of CD can also be represented by time. In the standard speed, the standard capacity is defined as 74 minutes.
High-capacity CD can play 80-minutes (equivalent to 700MB). There are also two kinds of rare large-capacity CDs for 90 minutes and 99 minutes.

CD-R is used to indicate the capacity in two ways, such as the disk shall be marked "74 minutes, 650MB". Actually, the time is accurate, but with the "MB" of representation, it is right when the disc is used as a data disc, but as other types of discs used, its capacity will be more than 650MB.

Here we would like to set audio CD, data CD, and video CD as examples, their capacity of sectors are 2352, 2048, 2236 byte and their capacity would be:
Audio CD: 74×60×75×2352÷1024÷1024=746.93(MB)
Data CD: 74×60×75×2048÷1024÷1024=650.39(MB)
Video CD: 74×60×75×2336÷1024÷1024=741.85(MB)