A new intraframe LSP interpolation technique for low bit rate speech coding

This paper presents a linear LSP interpolation between neighboring frames. Usually there are two to four formants in speech spectrum envelope, and the LSF(Line Spectral Frequency) parameters have an order property. In this paper, we divide the LSF parameters into three sub-vectors, and predict them by the vectors of previous and next frames. An efficient and reliable LSP vector distance measure is proposed for this interpolation algorithm. The interpolated LSP vectors are utilized in our mixed excitation LPC vocoder, which is operated at 1.5 kbps. Informal listening tests indicate that the synthesized speech sounds natural and intelligible.