A new fast two dimension 8×8 Inverse Discrete Cosine Transform (IDCT) algorithm based on Look-Up Table (LUT) is presented

in which

the LUT structure is based on the DCT basic images.The LUT size is decreased by using two techniques.One is to use the symmetries of the basic images;another is to elicit the range of each quantized DCT coefficient. As a result

the LUT only has 10.9746K data.If the quantization matrix has the symmetry

q(u

v)=q(v

u)

the LUT size can be decreased half nearly again.The new algorithm avoids multiplications by using LUT and decreases additions greatly by utilizing the characteristics of actual images and the symmetries of the basic images. The experimental results indicate that it only needs 182 additions av

eragely and decreases about 15 percent of additions besides eliminating multiplications compared with Feig’s algorithm that needs least arithmetic operations nowadays.