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Nasir Ahmed
Nasir Ahmed in 2012
Born	1940 (age 84–85) Bangalore,Kingdom of Mysore,British India
Education	Bishop Cotton Boys' School University of Visvesvaraya College of Engineering (BSc), University of New Mexico (MSc, PhD)
Known for	Discrete cosine transform (DCT) Inverse DCT (IDCT) DCTlossy compression DCTimage compression Lossless DCT (LDCT) Discrete sine transform (DST)
Spouse	Esther Parente-Ahmed
Children	Michael Ahmed Parente
Awards	1982  Distinguished Graduate Faculty Member AwardKansas State University 1985  IEEE Fellow 2001  Distinguished Engineering Alumnus AwardUniversity of New Mexico
Scientific career
Fields	Electrical Engineering Computer science
Thesis	Derivation Of Transfer Functions From Time Delay Specifications And Their Approximations (1966)
Doctoral advisor	Shlomo Karni

Nasir Ahmed (born 1940) is an American electrical engineer and computer scientist. He isProfessor Emeritus of Electrical and Computer Engineering atUniversity of New Mexico (UNM). He is best known for inventing thediscrete cosine transform (DCT) in the early 1970s. The DCT is the most widely useddata compression transformation, the basis for mostdigital media standards (image,video andaudio) and commonly used indigital signal processing. He also described thediscrete sine transform (DST), which is related to the DCT.^[1]

The discrete cosine transform (DCT) is alossy compression algorithm that was first conceived by Ahmed while working at theKansas State University, and he proposed the technique to theNational Science Foundation in 1972. He originally intended the DCT forimage compression.^[2][3] Ahmed developed a working DCTalgorithm with his PhD student T. Natarajan and friendK. R. Rao in 1973,^[2] and they presented their results in a January 1974 paper.^[4][5][6] It described what is now called the type-II DCT (DCT-II),^[7]: 51 as well as its inverse, the type-III DCT (a.k.a. IDCT).^[4]

Ahmed was the leading author of the benchmark publication,^[8][9]Discrete Cosine Transform (with T. Natarajan and K. R. Rao),^[4] which has been cited as a fundamental development in many works^[10] since its publication. The basic research work and events that led to the development of the DCT were summarized in a later publication by Ahmed entitled "How I came up with the Discrete Cosine Transform".^[2]

The DCT is widely used for digitalimage compression.^[11][12][13] It is a core component of the 1992JPEG image compression technology developed by theJPEG Experts Group^[14] working group and standardized jointly by theITU,^[15]ISO andIEC. A tutorial discussion of how it is used to achieve digitalvideo compression in various international standards defined byITU andMPEG (Moving Picture Experts Group) is available in a paper by K. R. Rao and J. J. Hwang^{[16]: JPEG: Chapter 8; H.261: Chapter 9; MPEG-1: Chapter 10; MPEG-2: Chapter 11} which was published in 1996, and an overview was presented in two 2006 publications byYao Wang.^[17][18] 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 asDCT-2 in the context of a family of discrete cosine transforms,^[19] or asDCT-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.^[20] 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" designs are conceptually similar to the conventional DCT but are simplified to provide exactly specified decoding with reducedcomputational complexity.

A DCT variant, themodified discrete cosine transform (MDCT), is used in modernaudio compression formats such asMP3,^[21]Advanced Audio Coding (AAC), andVorbis (OGG).

Thediscrete sine transform (DST) is derived from the DCT, by replacing theNeumann condition atx=0 with aDirichlet condition.^[7]: 35 The DST was described in the 1974 paper by Ahmed, Natarajan and Rao.^[4]

Ahmed later was involved in the development a DCTlossless compression algorithm with Giridhar Mandyam and Neeraj Magotra at theUniversity of New Mexico in 1995. This allows the DCT technique to be used forlossless compression of images. It is a modification of the original DCT algorithm, and incorporates elements of inverse DCT anddelta modulation. It is a more effective lossless compression algorithm thanentropy coding.^[22]

• Alumnus of theBishop Cotton Boys' School; received his B.S. degree in Electrical Engineering from theUniversity of Visvesvaraya College of Engineering,Bangalore in 1961;
• Received his M.S. and Ph.D. degrees in Electrical and Computer Engineering from theUniversity of New Mexico in 1963 and 1966, respectively. His doctoral dissertation adviser was Shlomo Karni;
• Principal Research Engineer,Honeywell, St. Paul, Minnesota 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, New Mexico, 1976–90.
• Married to Esther Parente-Ahmed. Son, Michael Ahmed Parente.

Inseason 5, episode 8 of NBC'sThis Is Us, Ahmed's story was told to highlight the importance of image and video transmission over the Internet in modern society, particularly during theCOVID-19 pandemic. The episode ends with a picture of Ahmed and his wife, along with captions explaining the importance of his work, and that producers spoke to the couple over video chat to understand their story and incorporate it into the episode.^[23]

• Nasir Ahmed publications indexed byGoogle Scholar
• IEEE Fellow in 1985, "for his contributions to engineering education and to digital signal processing" .[4].
• Distinguished Engineering Alumnus Award,University of New Mexico, 2001.[5]Archived 2 January 2020 at theWayback Machine.
• Distinguished Graduate Faculty Member Award,Kansas State University, 1982-83.[6].

• 1940 births
• 20th-century American inventors
• American electrical engineers
• American information theorists
• Bishop Cotton Boys' School alumni
• Fellows of the IEEE
• Indian computer scientists
• Indian electrical engineers
• Indian electronics engineers
• Indian emigrants to the United States
• 21st-century Indian inventors
• Internet pioneers
• Data compression researchers
• Living people
• University of New Mexico alumni
• University of New Mexico faculty
• University Visvesvaraya College of Engineering alumni

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