I am trying to digest this paper.
So far, I've been successful with DFT and DHT. Could someone give a hand with DCT?
I am trying to reproduce the convolution theorem for DCT-I and DCT-II. But my results never match the same as the result I get with DFT and DHT.
I am reading reference 9 of the paper
RAO, K. R.—YIP, P.: Discrete Cosine Transform — Algo- rithms, Advantages, Applications, Academic Press, Inc., Lon- don, 1990.
But it puts the conv. theorem of DCT-II in other terms.
I have also read other works, such as
 Martucci. Symmetric Convolution and the Discrete Sine and Cosine Transforms
 Roma. A tutorial overview on the properties of the discrete cosine transform for encoded image and video processing
and others. But I am interested on the Conv. Theorem on a similar fashion as the first two references.