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Definition

The MiniDisc system was introduced in the consumer audio market as a new digital audio playback and recording system. The introduction time was just ten years after the introduction of the Compact Disc (CD). As is known, CD has effectively replaced the vinyl LP records in the audio disc market. CD technology is based on 16-bit quantization and 44.1-kHz sampled digital audio recording. The CD sound quality was fairly improved compared to any consumer analog recording equipment.

Before starting the CD business, many engineers engaged in the development of the CD solely for its improvement in sound quality, but after the introduction of the CD player into the market, we found out that the consumer became aware of the quick random-access characteristic of the optical disc system. The next target of development was obviously to be the rewritable CD. Two different recordable CD systems were established. One is the write-once CD named CD-R and the other is the re-writable CD named CD-MO.

Sales of cassette tapes had been decreasing since 1989. Even if recordable CD were to be accepted by the consumer, it would still be difficult to break into the portable market. Here, portable compact cassette dominated because of its strong resistance to vibration and its compactness. Clear targets for a new disc system were to overcome these weaknesses. Sony was able to achieve this by introducing a disc system called MiniDisc (MD).
The name, MiniDisc (MD), comes from its size. MiniDisc was developed by as an audio media that combines the merits of both CD (supreme quality) and Tape (recordable). The disc, with a diameter of 64 mm and thickness of only 1.2 mm, is placed inside a cartridge of 72 X 68 X 5 mm.

The cartridge protects the disc from exposures and withstand forces eliminating problems that connects with CD (scratches) or tape (tangles). The Minidisc is based on Magneto-Optical technology, which is essentially a method of recording information by using a laser to alter magnetic information on the disc. In order to alter the information, the disc has to be heated to a high temperature, meaning that if left on a desk near a magnet, it should remain unaffected, unless you heat the disc to the required 180°C.

Types Of MiniDiscs
Premastered MiniDiscs are used most commonly for music and are sold in record stores just the same as compact cassettes and CDs are. Minidiscs, just like CDs, are manufactured in large volumes by high-speed injection molders, and the music signals are recorded during replication in the form of pits. Moreover, the discs are encased in a cartridge, so there is no worry about their being scratched. The design of the premastered Minidisc cartridges is special. Prerecorded music packages require a label, featuring the artist's picture or other information. Therefore the top face of the cartridge is left completely free for the label.

A window for the laser beam to read the disc is only necessary on the bottom face. Both a CD and a Minidisc can store the same amount of music. The difference is that a Minidisc uses a digital compression technique called ATRAC (Adaptive Transform Acoustic Coding) to compress audio data in 1:5 ratio by eliminating inaudible frequencies and faint background noises.

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