A mixed excitation LPC vocoder operating at very low bit rate

This paper presents a 1.2 kb/s mixed LPC vocoder based on multiband excitation (MBE) model. The vocoder extracts the pitch by a robust and efficient tracking algorithm. The cut-off frequency, which is a fundamental parameter in a mixed excitation system, is obtained by the v/uv decision of MBE analysis. In order to reduce the bit rate, the coder has used frame interpolation between neighboring frames. A fast and reliable linear interpolation algorithm is proposed. Informal listening tests indicate that for either clean speech or telephone speech, the synthesized speech sounds natural and intelligible, and the quality is better than that of 2.4 kb/s LPC-10e standard