• The Rewritable MiniDisc System
  Proceedings of the IEEE, USA vol. 82 no. 10 pp. 1492-1500, Oct 1994
  T. Yoshida (Sony)
  The MiniDisc system was designed with the obvious objective of replacing the conventional Compact Cassette tape recorder system. The MiniDisc format defines two types of optical discs. One is a recordable magneto-optical disc for user recording and another is a conventional read-only disc for music-software publishing. Audio data compression is used to achieve 74 min of playing time on a 64-mm disc. By means of a built-in buffer memory called Shock Resistant Memory, MiniDisc can be used for outdoor portable applications with great ease. Furthermore, MiniDisc was evolved into the MD Data system and with a data capacity of 140 Mbytes and a very compact size, the MD Data system is expected to become one of the standards for removable data storage systems.

• MiniDisc: Successful Innovation or Just Cool Technology? -- An Analysis of Sony's Decade-Long Quest for Success
  DSES 6470, "Strategic Management of Technology and Innovation" Rensselaer Polytechnic Institute Troy, NY
  E. Paul Ratazzi
  The result of a successful innovation process is a commercially successful product that pays back investments in development and marketing, and eventually yields a profit for the original innovator. The development and subsequent marketing of the Sony MiniDisc (MD) system provides an excellent framework in which to study this process and the factors contributing to its outcome. This report begins with a background that describes the market, industry, and technological contexts in which the MD concept was born. MD?s key performance characteristics are identified and compared to a rival technology that was simultaneously introduced into the market. This is followed by a chronological tracing of Sony?s effort to commercialize the MD ? an effort which began in 1992 and continues to this day. The case is then analyzed in the following three contexts: 1) integration of technology and strategy, 2) design, enactment, and evolution of technology strategy, and 3) innovation challenges. The main conclusion of the analysis is that Sony?s technological competencies, complementary assets, identification of emerging markets, and product reinvention efforts all contributed, over a lengthy period of time, to the eventual success of the MD format.

• ATRAC: Adaptive Transform Acoustic Coding For Minidisc
  Presented at the Audio Engineering Society 93rd Conv., Oct. 1992.
  K. Tutui, H. Suzuki, O. Shimoyoshi, M. Sonohara, K. Akagiri, and R. M. Heddie (Sony)
  ATRAC is an audio coding system based on psychoacoustic principles. The input signal is divided into three subbands which are then transformed into the frequency domain using a variable block length. Transform coefficients are grouped into nonuniform bands to reflect the human auditory system, and then quantized on the basis of dynamic sensitivity and masking characteristics. ATRAC compresses compact disc audio to approximately 1/5 of the original data rate with virtually no loss in sound quality.

• An Audio Codec For Multiple Generations Compression Without Loss Of Perceptual Quality
  Proceedings of the AES 17^th International Conference on High Quality Audio Coding, Florence, Italy. 1999
  Frank Kurth, University of Bonn, Bonn, Germany
  [Contains a detailed explanation of the causes of generational loss in perceptual coders]
  We describe a generic audio codec allowing for multiple, i.e., cascaded, lossy compression without loss of perceptual quality as compared to the first generation of compressed audio. For this sake we transfer encoding information to all subsequent codecs in a cascade. The supplemental information is embedded in the decoded audio signal without causing degradations. The new method is applicable to a wide range of current audio codecs as documented by our MPEG-1 implementation.

• Magneto-Optical Recording Systems (Minidisc Section)
  Chapter 10 Magneto-Optical Recording Materials, ISBN: 0-7803-1009-8, August 1999
  R. Gambino, T. Suzuki (Ed.)
  (An technical overview of the Minidisc system with a particularly detailed look at its Magneto-Optical system)

• Domain Wall Displacement Detection Mini Disc with Land/Groove Recording Applied to Mini Disc Systems
  Jpn. J. Appl. Phys. Vol.41 (2002) pp. 1643-1646
  Goro Fujita, Tetsuhiro Sakamoto, Ariyoshi Nakaoki, Yoshiyuki Teraoka and Sohmei Endoh (Sony)
  We confirmed a wide tolerance and capability of over 2.0 GB/64 mmv, equivalent to 14 times the capacity of Mini Disc (MD) using a combination of domain wall displacement detection (DWDD) and land/groove recording and by optimizing groove geometry and surface treatment.

• Anneal-less Domain Wall Displacement Detection of 15 Gbit/in² land-groove recording using a deep groove substrate and a red laser
  Optical Data Storage 2003, SPIE Vol. 5069 (2003)
  Tetsuhiro Sakamoto*, Yasuhito Tanaka, Shingo Imanishi, Motohiro Furuki, Nobuyuki Arakawa, Kazuhiko Fujiie (Sony)
  Domain Wall Displacement Detection (DWDD) medium with no annealing method, which we call "anneal-less" DWDD medium, has been improved for practical use. The key technologies of our progress are not only an optimum design of the magnetic film structure but also a deep groove substrate for land-groove recording with a quite unique groove form. The substrate was prepared by using the mastering process with a reactive ion etching (RIE) method. We achieved 15 Gbit/in²-areal density with wide system tolerances using the anneal-less DWDD medium, a 660nm-laser and a 0.60 NA objective lens. The areal density corresponds to 4.7 GB-capacity on a disc like MiniDiscTM (MD) with a 64 mmdiameter.

• 15 Gbit/in² recording on a DWDD disc using a land/groove substrate with a red laser enabled by a side-wall-annealing process
  Optical Data Storage 2003, SPIE Vol. 5069 (2003)
  Takeshi Miki, Shirnchi Kai, Yasuyuki Takeshita, Goro Fujita, Kazuhiko Fujue (Sony)
  Osamu Koyama, Yasuyuki Miyaokac, Tomoyuki Hirokic, Yasushi HOzumi, Masaru Kikuchi', Tsutomu Shiratori (Canon)
  We developed a side-wall-annealing technique for land/groove substrates. By applying this technique to our Domain Wall Displacement Detection (DWDD) Magneto-Optical (MO) recording stack formed on a landlgroove substrate, even with an NA of 0.6 and a wavelength of 660 nm, we realized a density of 15 Gbit/in² with a sufficiently wide recording tolerance. This density corresponds to a capacity of 4.7 GB on a 64 mm disc like MiniDisc.

• IP Cell for Error Correction Systems in Minidisc
  IEEE Transactions on Consumer Electronics, Vol. 45, No. 1 Feb, 2000
  A. De Gloria, D. Grosso, M. Oddicini and F. Sciutto., University of Genoa, Italy
  An error correction system based on the Advanced Reed Solomon Code (ACIRC) has been studied and implemented. We modelled the whole structure of a Minidisc (MD) player through a methematical simulator. We tested our hardware implementat of the ACIRC decoder inserted in the global structure through co-simulations. The final result has been the design of a reusable firm core implementating the functions of the ACIRC decoder block.

• ATRAC3plus Listening Tests and Technical Measurements
  ITS Research & Testing Centre Technical Report A.61346, pp. 29, Feb. 2003
  R. Brooker, F. Henderson
  ITS-RTC were requested by Sony Europe BV to conduct some listening tests to compare a new Sony digital audio CODEC system (ATRAC3plus) with two established CODEC systems: MP3 and WMA (version 9). The tests were to mirror tests already carried out by Sony in order to provide independent confirmation of their findings. The tests were designed specifically to compare the Sony system against the other two systems at different bit-rates. 132Kbps ATRAC3 was also compared to the two other CODEC systems at a high data rate only.

• Listening Test Report for Sony Europe BV
  Testfactory, Stuttgart, Germany, Feb. 2003
  Sony ATRAC3plus 48kbps as used by Sony compared with MP3 48kbps, (Fraunhofer-Type as included in CoolEdit Pro 2.0) and WMA 48kbps (MS-WMEncoder version 9.0). Sony ATRAC3plus 64kbps compared with MP3 64kbps and WMA 64kbps. Sony ATRAC3 132kbps compared with MP3 128kbps and WMA 128kbps. Sony ATRAC3plus 64kbps compared with MP3 128kbps.

• A Comparison of the ATRAC and MPEG-1 Layer 3 Audio Compression Algorithms
  Christopher Hoult, University of Southampton, Nov. 2002
  This paper intends to give the reader some insight into the workings of ATRAC and MPEG-1 Layer 3 and to compare the two approaches to audio compression. ATRAC is used in MiniDisc technology, while MPEG-1 Layer 3 is used extensively as an allpurpose software audio compression technique.

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