Indian-American electrical engineer and computer scientist (born 1940)
Nasir Ahmed
|
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Nasir Ahmed in 2012
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Born
| 1940
(84 years ago)
(
1940
)
|
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Nationality
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---|
Education
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Known for
| |
---|
Spouse
| Esther Parente-Ahmed
|
---|
Children
| Michael Ahmed Parente
|
---|
Awards
| |
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Scientific career
|
Fields
| |
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Thesis
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Doctoral advisor
| Shlomo Karni
|
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|
Nasir Ahmed
(born 1940) is an Indian-American electrical engineer and computer scientist. He is
Professor Emeritus
of Electrical and Computer Engineering at
University of New Mexico
(UNM). He is best known for inventing the
discrete cosine transform
(DCT) in the early 1970s. The DCT is the most widely used
data compression
transformation, the basis for most
digital media
standards (
image
,
video
and
audio
) and commonly used in
digital signal processing
. He also described the
discrete sine transform
(DST), which is related to the DCT.
[1]
Discrete cosine transform (DCT)
[
edit
]
The discrete cosine transform (DCT) is a
lossy compression
algorithm that was first conceived by Ahmed while working at the
Kansas State University
, and he proposed the technique to the
National Science Foundation
in 1972. He originally intended the DCT for
image compression
.
[2]
[3]
Ahmed developed a working DCT
algorithm
with his PhD student T. Natarajan and friend
K. 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 digital
image compression
.
[11]
[12]
[13]
It is a core component of the 1992
JPEG
image compression technology developed by the
JPEG Experts Group
[14]
working group and standardized jointly by the
ITU
,
[15]
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
[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 by
Yao 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:
Standard
|
Technologies
|
JPEG
|
Storage and transmission of photographic images on the World Wide Web (
JPEG
/
JFIF
); and widely used in digital cameras and other photographic image capture devices (
JPEG
/
Exif
).
|
MPEG-1
Video
|
Video distribution on CD or via the World Wide Web.
|
MPEG-2 Video
(or
H.262
)
|
Storage and handling of digital images in broadcast applications: digital TV, HDTV, cable, satellite, high speed internet; video distribution on DVD.
|
H.261
|
First of a family of video coding standards (1988). Used primarily in older video conferencing and video telephone products.
|
H.263
|
Videotelephony
and
videoconferencing
|
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,
[19]
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.
[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 reduced
computational complexity
.
Standard
|
Technologies
|
VC-1
|
Windows media video 9,
SMPTE 421
.
|
H.264/MPEG-4 AVC
|
The most commonly used format for recording, compression and distribution of high definition video; streaming internet video; Blu-ray Discs; HDTV broadcasts (terrestrial, cable and satellite).
|
H.265/HEVC
|
Successor to the H.264/MPEG-4 AVC standard having substantially improved compression capability.
|
H.266/VVC
|
Successor to HEVC having substantially improved compression capability.
|
WebP
Images
|
A graphic format that support the lossy compression of digital images. Developed by
Google
.
|
WebM
Video
|
A multimedia open source format intended to be used with HTML5. Developed by Google.
|
A DCT variant, the
modified discrete cosine transform
(MDCT), is used in modern
audio compression
formats such as
MP3
,
[21]
Advanced Audio Coding
(AAC), and
Vorbis
(OGG).
The
discrete sine transform
(DST) is derived from the DCT, by replacing the
Neumann condition
at
x=0
with a
Dirichlet 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 DCT
lossless compression
algorithm with Giridhar Mandyam and Neeraj Magotra at the
University of New Mexico
in 1995. This allows the DCT technique to be used for
lossless compression
of images. It is a modification of the original DCT algorithm, and incorporates elements of inverse DCT and
delta modulation
. It is a more effective lossless compression algorithm than
entropy coding
.
[22]
Background
[
edit
]
- Alumnus of the
Bishop Cotton Boys' School
; received his B.S. degree in Electrical Engineering from the
University Visvesvaraya College of Engineering
,
Bangalore
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 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.
Books
[
edit
]
Popular culture
[
edit
]
In
season 5
, episode 8 of NBC's
This Is Us
, Ahmed's story was told to highlight the importance of image and video transmission over the Internet in modern society, particularly during the
COVID-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]
References
[
edit
]
- ^
"Who is Nasir Ahmed? Real love story of Indian-American engineer on 'This Is Us' who is credited for .jpg algorithm"
.
meaww.com
. Retrieved
8 April
2022
.
- ^
a
b
c
Ahmed, Nasir
(January 1991).
"How I Came Up With the Discrete Cosine Transform"
.
Digital Signal Processing
.
1
(1): 4?5.
doi
:
10.1016/1051-2004(91)90086-Z
.
- ^
Stankovi?, Radomir S.; Astola, Jaakko T. (2012).
"Reminiscences of the Early Work in DCT: Interview with K.R. Rao"
(PDF)
.
Reprints from the Early Days of Information Sciences
.
60
. Tampere International Center for Signal Processing.
ISBN
978-9521528187
.
ISSN
1456-2774
.
Archived
(PDF)
from the original on 30 December 2021
. Retrieved
30 December
2021
– via
ETHW
.
- ^
a
b
c
d
—; Natarajan, T. Raj;
Rao, K.R.
(1 January 1974). "Discrete Cosine Transform".
IEEE Transactions on Computers
.
C-23
(1). IEEE Computer Society: 90?93.
doi
:
10.1109/T-C.1974.223784
.
eISSN
1557-9956
.
ISSN
0018-9340
.
LCCN
75642478
.
OCLC
1799331
.
S2CID
39023640
.
- ^
Rao, K. Ramamohan
; Yip, Patrick C. (11 September 1990).
Discrete Cosine Transform: Algorithms, Advantages, Applications
. Signal, Image and Speech Processing.
Academic Press
.
arXiv
:
1109.0337
.
doi
:
10.1016/c2009-0-22279-3
.
ISBN
978-0125802031
.
LCCN
89029800
.
OCLC
1008648293
.
OL
2207570M
.
S2CID
12270940
.
- ^
"T.81 ? Digital compression and coding of continuous-tone still images ? requirements and guidelines"
(PDF)
.
CCITT
. September 1992
. Retrieved
12 July
2019
.
- ^
a
b
Britanak, Vladimir; Yip, Patrick C.;
Rao, K. R.
(6 November 2006).
Discrete Cosine and Sine Transforms: General Properties, Fast Algorithms and Integer Approximations
.
Academic Press
.
ISBN
978-0123736246
.
LCCN
2006931102
.
OCLC
220853454
.
OL
18495589M
.
S2CID
118873224
.
- ^
Selected Papers on Visual Communication:
Technology and Applications
, (SPIE Press Book), Editors T. Russell Hsing and Andrew G. Tescher, April 1990, pp. 145-149
[1]
.
- ^
Selected Papers and Tutorial in Digital Image Processing and Analysis, Volume 1,
Digital Image Processing and Analysis
, (IEEE Computer Society Press), Editors R. Chellappa and A. A. Sawchuk, June 1985, p. 47.
- ^
DCT citations via Google Scholar
[2]
.
- ^
Andrew B. Watson (1994).
"Image Compression Using the Discrete Cosine Transform"
(PDF)
.
Mathematica Journal
.
4
(1): 81?88.
- ^
image compression
.
- ^
Transform coding
.
- ^
Wallace, G. K. (February 1992).
"The JPEG Still Image Compression Standard"
(PDF)
.
IEEE Transactions on Consumer Electronics
.
38
(1).
doi
:
10.1109/30.125072
.
.
- ^
CCITT 1992
[3]
.
- ^
Rao, K. R.
; Hwang, J. J. (18 July 1996).
Techniques and Standards for Image, Video, and Audio Coding
. Prentice Hall.
ISBN
978-0133099072
.
LCCN
96015550
.
OCLC
34617596
.
OL
978319M
.
S2CID
56983045
.
- ^
Yao Wang, Video Coding Standards: Part I, 2006
- ^
Yao Wang, Video Coding Standards: Part II, 2006
- ^
Gilbert Strang (1999).
"The Discrete Cosine Transform"
(PDF)
.
SIAM Review
.
41
(1): 135?147.
Bibcode
:
1999SIAMR..41..135S
.
doi
:
10.1137/S0036144598336745
.
- ^
Lee, Jae-Beom; Kalva, Hari (2008).
The VC-1 and H.264 Video Compression Standards for Broadband Video Services
. Springer Science+Business Media, LLC. pp. 217?245.
- ^
Guckert, John (Spring 2012).
"The Use of FFT and MDCT in MP3 Audio Compression"
(PDF)
.
University of Utah
. Retrieved
14 July
2019
.
- ^
Mandyam, Giridhar D.; Ahmed, Nasir; Magotra, Neeraj (17 April 1995). Rodriguez, Arturo A.; Safranek, Robert J.; Delp, Edward J. (eds.).
"DCT-based scheme for lossless image compression"
.
Digital Video Compression: Algorithms and Technologies 1995
.
2419
.
SPIE
: 474?478.
Bibcode
:
1995SPIE.2419..474M
.
doi
:
10.1117/12.206386
.
S2CID
13894279
.
- ^
Mizoguchi, Karen (16 February 2021).
"How This Is Us Honored the Real-Life 'Genius' Who Made It Possible for the Pearsons to Stay Connected amid COVID"
.
People.com
. Retrieved
21 March
2022
.
External links
[
edit
]