Initial codebook method of vector quantisation in Hadamard domain

To deal with the problem that the initialisation method based on random selection may provide a suboptimal codebook of vector quantisation (VQ); an improved method is proposed. In the proposed method, Hadamard transform is performed on training vectors, and then the transformed vectors are sorted according to their first elements. The ordered transformed vectors are partitioned into groups. The initial codebook is composed of the mid vector of each ordered group. This method has a better performance and can be used as the initialisation method of VQ to improve and speed up codebook design.