A very low complexity VSELP speech coder using regular pulse basis vectors

This paper describes a new Vector Sum Excited Linear Prediction (VSELP) coder with very low complexity. The method, called regular pulse VSELP (RP-VSELP), is based on regular pulse basis vectors with mutually orthonormal property. In this Approach, a very efficient vector-sum codebook is constructed from a set of mutually orthonormal regular pulse bassis vectors and enables us to simplify the codebook search without additional degradation of synthesized speech compared with that of the conventional VSELP. The regular pulse basis vectors are explicitly orthonormalized by means of the Gram-Schmidt procedure. To enhance the speech quality of the RP-VSELP speech coder, perceptually weighted distortion measure between the input and the synthesized speech is utilized in an iterative closed-loop training process of the regular pulse basis vectors. It is shown that speech quality is improved by the training process. Experimental results demonstrate that the proposed method produces the synthesized speech quality comparable to that of the VSELP scheme at the bit-rate of 4.8 Kbps.