Type (IV) Discrete Cosine Xform
c = dct_iv(x)
1-d signal, length(x) = 2^J
1-d cosine transform, length(x)=2^J
The form c = dct_iv(x) computes c defined by c_m = sqrt(2/N) * sum_n x(n) cos( pi * (m-.5) * (n-.5) / N ) where 1 <= m,n <= N, N = length(x) = length(c)
To reconstruct, use the same function: x = dct_iv(c)