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The Inventor of DCT: How Dr. Nasir Ahmed Changed Digital Media
The Man Who Shrank the Digital World
Series: Sampada 30 Days Special Edition
Every time you engage in a Zoom call, binge-watch a series on Netflix, or simply upload a selfie to Instagram, you are relying on a piece of mathematics developed by a graduate of our very own college.
This is the story of Dr. Nasir Ahmed, a 1961 UVCE alumnus, and the Discrete Cosine Transform (DCT)—the algorithm that made the modern digital media revolution possible.
A UVCEian at the Heart of the Revolution
It is a matter of immense pride for the University Visvesvaraya College of Engineering (UVCE) that one of the most influential figures in the history of computer science walked our corridors. Dr. Nasir Ahmed graduated with a Bachelor of Engineering in Electrical Engineering from UVCE in 1961.
Like many of us, he started his journey in the classrooms of KR Circle. After graduating from UVCE, he went on to pursue higher education in the United States, earning his M.S. and Ph. D. degrees from the University of New Mexico (UNM) in 1963 and 1966, respectively. While his academic career flourished abroad, establishing him as a Professor Emeritus at UNM, his foundational years as an engineer were shaped right here in Bangalore.
The Problem: Data was Too Big
To understand the magnitude of Dr. Ahmed’s invention, we have to look at the world of computing in the early 1970s. At that time, storing and transmitting images was a nightmare. Computers dealt with "spatial domain" data—essentially a massive grid of pixels.
If you wanted to send a high-quality image over the internet (or the primitive networks of that time), it required an enormous amount of bandwidth and storage space. Engineers knew they needed a way to compress these files without losing too much quality, but the existing methods, like the Fourier Transform, were too computationally heavy and inefficient for images.
"We needed a way to pack more information into fewer bits. The world was waiting for a compression standard, even if they didn't know it yet."
The Invention: Discrete Cosine Transform (DCT)
In 1974, Dr. Nasir Ahmed, along with his colleagues T. Natarajan and K.R. Rao, published a landmark paper titled "Discrete Cosine Transform". This paper proposed a new algorithm that would change everything.
What is DCT? In simple terms, DCT takes an image and breaks it down into "frequencies." It realizes that in most photos, large areas of color don't change much. DCT groups the important visual information (low frequencies) and discards the invisible noise (high frequencies) that the human eye can't really see anyway.
This allows for Lossy Compression—making the file size up to 100 times smaller while looking nearly identical to the original.
Click the button to see which technologies depend on Dr. Ahmed's DCT algorithm!
Comparing the Titans: DCT vs. The Rest
Before DCT, the primary method for signal processing was the Discrete Fourier Transform (DFT). While DFT is powerful, it wasn't perfect for images. Let's look at why Dr. Ahmed's solution was superior for digital media.
| Feature | Discrete Fourier Transform (DFT) | Discrete Cosine Transform (DCT) |
|---|---|---|
| Basis Functions | Uses Sines and Cosines (Complex Numbers) | Uses only Cosines (Real Numbers) |
| Energy Compaction | Good, but spreads energy | Excellent (packs info into fewer coefficients) |
| Computational Load | High (Complex arithmetic) | Lower (Real arithmetic only) |
| Primary Usage | Signal Analysis, Radar, Audio | Image/Video Compression (JPEG, MPEG) |
The "Godfather" of the JPEG and MP3
It took a few years for the world to catch up, but once digital media began to take off in the late 80s and 90s, DCT became the gold standard.
- JPEG: The Joint Photographic Experts Group adopted DCT as the core of the JPEG standard in 1992. Every time you save a photo as a .jpg, you are running Dr. Ahmed's algorithm.
- MPEG: Video requires even more compression than images. The Moving Picture Experts Group (MPEG) used DCT to create the standards that allow for DVDs, Digital TV, and streaming.
- MP3: The Modified Discrete Cosine Transform (MDCT), a variant of Dr. Ahmed’s work, is the basis for MP3 audio compression and AAC (used by Apple).
Recognition and Legacy
Dr. Nasir Ahmed is not just a footnote in history; he is a celebrated figure in the engineering world. He was named an IEEE Fellow in 1985 for his contributions to engineering education and digital signal processing. He also authored the benchmark publication on DCT, which remains one of the most cited works in the field.
As students of UVCE, we often walk past the red heritage buildings without realizing the global impact of those who walked there before us. Dr. Ahmed is a prime example of how a foundation built at UVCE can lead to innovations that touch the lives of billions of people every single day.
A Message to the Current Batch
In an era of AI, Generative Models, and Cloud Computing, it is easy to forget the fundamental algorithms that make it all run. However, the spirit of innovation remains the same. Whether you are coding a new app for CodeFury, presenting a paper at Kagada, or working on a project in the Quadrangle, remember that you are part of a lineage of innovators.
Dr. Nasir Ahmed didn't just invent an algorithm; he invented a way for the world to share memories. As we celebrate the Sampada 30 Days Series, let us take inspiration from his journey. From UVCE 1961 to the screens of 2025, the legacy continues.
This article is part of the special series by VisionUVCE & Sampada Team celebrating the rich history and future of our institution.