to understand the Algorithm go to matlab help in page dct2 and idct2 to get the mathematical expression



for M = N = 8, we can calculate the most of hard values and save it as LUTs to speed up the execution



now compare our special 8X8 functions with the internal general functions



use this code:



A = int32(100*rand(8,8))

tic for i = 1 : 1000 IDCT_8X8(DCT_8X8(A)) end toc

tic for i = 1 : 1000 idct2(dct2(A)) end toc



i had built the general functions too, but with low speed