The following Matlab project contains the source code and Matlab examples used for circular convolution using dct and dst.
Matlab code for the algorithm published in
V. G. Reju, S. N. Koh and I. Y. Soon, Convolution Using Discrete Sine and Cosine Transforms, IEEE Signal Processing Letters, VOL. 14, NO. 7, JULY 2007, pp.445-448.