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N Ahmed

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Name
  
N. Ahmed


N. Ahmed

Books
  
Discrete-time Signals and Systems

JKL | State of The Nation; Talking with Ahmednassir Abdullahi [Part 1]


Nasir Ahmed (born 1940 in Bangalore, India) is a Professor Emeritus of Electrical and Computer and Engineering at University of New Mexico (UNM). He is best known for the development of the discrete cosine transform (DCT), which is a data compression transformation.

Contents

Fundamental contribution: Discrete Cosine Transform (DCT)

Ahmed was the leading author of the benchmark publication, Discrete Cosine Transform (with T. Natarajan and K. R. Rao), which has been cited as a fundamental development in many works since its publication. The basic research work and events that led to the development of the DCT were summarized in a later publication by N. Ahmed, "How I came up with the Discrete Cosine Transform".

The DCT is widely used for digital image compression. It is a core component of the 1992 JPEG image compression technology developed by the JPEG Experts Group working group and standardized jointly by the ITU, ISO and IEC. A tutorial discussion of how it is used to achieve digital video compression in various international standards defined by ITU and MPEG (Moving Picture Experts Group) is available in a paper by K. R. Rao and J. J. Hwang which was published in 1996, and an overview was presented in two 2006 publications by Yao Wang. The image and video compression properties of the DCT resulted in its being an integral component of the following widely used international standard technologies:

The form of DCT used in signal compression applications is sometimes referred to as "DCT-2" in the context of a family of discrete cosine transforms, or as "DCT-II".

More recent standards have used integer-based transforms that have similar properties to the DCT but are explicitly based on integer processing rather than being defined by trigonometric functions. As a result of these transforms having similar symmetry properties to the DCT and being, to some degree, approximations of the DCT, they have sometimes been called "integer DCT" transforms. Such transforms are used for video compression in the following technologies pertaining to more recent standards:

The "integer DCT" design is conceptually similar to the conventional DCT; however, it is simplified and made to provide exactly specified decoding.

The DCT has been widely cited in patents that have been awarded since 1976, as evident from the following results corresponding to various search scenarios:

  • U.S. Patents Quick Search: Title: DCT. Description/Specification: Video [6];
  • U. S. Patent Quick Search: Title: Image. Abstract: DCT [7];
  • U. S Patent Quick Search: Title: Video. Abstract: DCT [8];
  • U.S. Patent Quick Search: Title: Image. Description/Specification: DCT [9];
  • U.S. Patent Quick Search: Title: Video. Description/Speification: DCT [10].

    • Background

  • Alumnus of the Bishop Cotton Boys' School; received his B.S. degree in Electrical Engineering from the University Visvesvaraya College of Engineering, Bangalore, India in 1961;
  • Received his M.S. and Ph.D. degrees in Electrical and Computer Engineering from the University of New Mexico in 1963 and 1966, respectively. His doctoral dissertation adviser was Dr. Shlomo Karni;
  • Principal Research Engineer, Honeywell, St. Paul, MN from 1966–68;
  • Professor, Electrical and Computer Engineering Department, Kansas State University, 1968–83;
  • 1983-2001: University of New Mexico—Presidential Professor of Electrical and Computer Engineering, 1983–89; Chair, Department of Electrical and Computer Engineering, 1989–94; Dean of Engineering, 1994–96; Associate Provost for Research and Dean of Graduate Studies, 1996–2001;
  • Consultant, Sandia National Laboratories, Albuquerque, NM, 1976–90.

    • Books

    Have been translated into Russian, Chinese and Japanese:

  • Leading author of Orthogonal Transforms for Digital Signal Processing, Springer-Verlag (Berlin – Heidelberg – New York), 1975, with K.R. Rao; translated into Russian (1980) and Chinese (1979). It is the first text book that included the DCT, and one of the first to present a unified approach to using sinusoidal and non-sinusoidal orthogonal transforms for signal processing. To quote one reviewer, "the authors have treaded where others have feared to venture. In doing so, they have developed a useful book as a first effort in the exciting area of digital signal processing and general orthogonal transforms;" for details, see H. Andrews [11].

    • It continues to be cited with respect to a broad spectrum of signal processing applications—see Google-Scholar citations [12] . Available in approximately 230 libraries. A softcover reprint of this first edition is now available—e.g., see Springer-Verlag, Amazon, Barnes and Noble and Alibris.

  • Leading author of Discrete-Time Signals and Systems, Reston Publishing Company, Inc. (A Prentice-Hall Company), Reston, Virginia, 1983, with T. Natarajan; translated into Japanese (1990). Available in approximately 215 libraries.

    • References

    N. Ahmed Wikipedia
    (Text) CC BY-SA


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