Vector quantization(VQ) is an efficient approach of lossy data compression. The performance of the fast codeword search algorithm in VQ determines its encoding time. Absolute error inequality(AEI) algorithm is a standard fast codeword search algorithm

in which the initial matching codeword search is based on Minimax method. However

the computation cost that is required at this step in AEI algorithm is too much. Aimed at solving this problem

we propose an improved method for searching the initial matching codeword that is named as Partial Minimax Method. The proposed method guarantees the found initial matching codeword is the same as the standard AEI method and the PSNR performance of AEI method has no degradation. Because it can significantly reduce the computational cost for searching the initial matching codeword

the proposed method can speed up the standard AEI method effectively.