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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. ==Fundamental contribution: Discrete Cosine Transform (DCT)== Ahmed was the leading author of the benchmark publication,〔Selected Papers on Visual Communication: ''Technology and Applications'', (SPIE Press Book), Editors T. Russell Hsing and Andrew G. Tescher, April 1990, pp. 145-149 ().〕〔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.〕 ''Discrete Cosine Transform'' (with T. Natarajan and K. R. Rao), which has been cited as a fundamental development in many works〔DCT citations via Google Scholar ().〕 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".〔(【引用サイトリンク】title=How I Came Up With the Discrete Cosine Transform )〕 The DCT is widely used for digital ''image'' compression.〔(【引用サイトリンク】title=Image Compression Using the Discrete Cosine Transform )〕〔image compression.〕〔Transform coding.〕 It is a core component of the 1992 JPEG image compression technology developed by the JPEG Experts Group〔G. K. Wallace, JPEG 1992 ().〕 working group and standardized jointly by the ITU,〔CCITT 1992 ().〕 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〔K. R. Rao and J. J. Hwang, ''Techniques and Standards for Image, Video, and Audio Coding'', Prentice Hall, 1996; 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.〔(Yao Wang, Video Coding Standards: Part I, 2006 )〕〔(Yao Wang, Video Coding Standars: Part II, 2006 )〕 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,〔(【引用サイトリンク】title=The Discrete Cosine Transform, )〕 or as "DCT-II".〔Discrete cosine transform.〕 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.〔Jae-Beom Lee and Hari Kalva, ''The VC-1 and H.264 Video Compression Standards for Broadband Video Services'', Springer Science+Business Media, LLC., 2008, pp. 217-245; for more on this book, see ()〕 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 (); *U. S. Patent Quick Search: Title: Image. Abstract: DCT (); *U. S Patent Quick Search: Title: Video. Abstract: DCT (); *U.S. Patent Quick Search: Title: Image. Description/Specification: DCT (); *U.S. Patent Quick Search: Title: Video. Description/Speification: DCT (). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「N. Ahmed」の詳細全文を読む スポンサード リンク
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