DCT/inverse DCT arithmetic unit using both of a first and second different algorithm to thereby provide an improved combination of speed and accuracy

摘要

In a DCT (discrete cosine transformation)/inverse DCT arithmetic unit, data of an inputted image are inputted to a first one- dimensional N-th order DCT/inverse DCT arithmetic device using a first algorithm B. The first one-dimensional N-th order DCT/inverse DCT arithmetic device calculates a one-dimensional N-th order inverse DCT. Calculated results of the first one-dimensional N-th order DCT/inverse DCT arithmetic device are stored to a memory for intermediate results as intermediate results of the N-th order inverse DCT in M-dimensions. Similarly, a second one- dimensional N-th order DCT/inverse DCT arithmetic device calculates a one- dimensional N-th order inverse DCT using a second algorithm A, with stored data of the memory for intermediate results as an input. Calculated results of the second one- dimensional N-th order DCT/inverse DCT arithmetic device are outputted to the memory for intermediate results. Similarly, an M-th one-dimensional N- th order DCT/inverse DCT arithmetic device calculates a one-dimensional N- th order DCT/inverse DCT. Calculated results finally obtained by the M-th one-dimensional N-th order DCT/inverse DCT arithmetic device are set as output data, This DCT/inverse DCT arithmetic unit has a high arithmetic operation speed and a high arithmetic accuracy.