 He, along with two other researchers, N. Ahmed and T. Natarajan, introduced the discrete cosine transform (DCT) in 1975 which has since become very popular in digital signal processing.DCT, INTDCT, directional DCT and MDCT (modified DCT) have been adopted in several international video/image/audio coding standards such as JPEG/MPEG/H.26X series and also by SMPTE (VC-1) and by AVS China.He is the co-author of the books "Orthogonal Transforms for Digital Signal Processing" (Springer-Verlag, 1975), Also recorded for the blind in Braille by the Royal Institute for the blind.