Inverse discrete cosine transform unit and discrete cosine transform unit

摘要

PROBLEM TO BE SOLVED: To make the circuit scale small and to effectively reduce the power consumption. SOLUTION: The discrete cosine converting device comprises a 1st arithmetic means composed of a 1st adding and subtracting means which performs the addition and subtraction of N pieces of data and a 2nd adding and subtracting means which performs the addition and subtraction of its outputs, a 2nd arithmetic means composed of a matrix arithmetic means which divides N arithmetic results outputted by the 1st arithmetic means into four groups of matrix data of N/4 rows by one column and multiplies the respective groups of matrix data by a coefficient matrix of N/4 rows by N/4 columns, and a 3rd arithmetic means composed of a 3rd adding and subtracting means which performs the addition and subtraction of N/2 arithmetic results among N arithmetic results outputted by the 2nd arithmetic means and a 1st multiplying means which multiplies the arithmetic results outputted therefrom. The reverse discrete cosine converting device can be constituted having nearly the same constitution.