3D DCT basis matrix in Matlab

Hi,

I am working in compressive sensing, lets say I have video blocks size 7x7x20, 7x7 image patchs and 20 frames each block.

I need the 3D DCT basis matrix in order to work with this blocks, I don't need to perform the transform I just need the elements of the basis.

For 2D I've been doing:

D1 = dctmtx(7);
D2 = kron(D1,D1);

This gives me the 2D DCT basis matrix that allows me to work with 7x7 image patches, now I need to extend this to 7x7x20 video blocks and I'm not sure how should I do it.

Thank you in advance.

[Firman]

Hi, there is a great code for applying N-dimensional DCT. You can find it here.