Windowing the discrete cosine transform in the transform domain

When processing a signal or an image using the Discrete Cosine Transform (DCT) or Discrete Sine Transform (DST), a typical approach is to extract a portion of the signal by windowing and then form the DCT or DST of the window contents. In this paper, an algorithm is developed to apply Hanning, Hamming, Blackman and related windows directly in the transform domain, for the DCT and DST. Software implementations in the C language are given. Examples of applications where this algorithm would be useful include data communication, adaptive system identification and filtering, real-time analysis of financial market data, etc.