Enhanced harmonic coding of speech with frequency domain transition modelling

A major source of audible distortion in current low-bit-rate harmonic speech coding algorithms is the ineffective modeling of the transitional speech signals such as onsets, plosives, etc. A new method of modeling transitional speech based on a frequency domain approach is introduced in this paper. The approach uses a modified harmonic model able to produce non-periodic pulse sequences in conjunction with a closed-loop analysis-by-synthesis scheme for parameter estimation and quantization. The structure of a speech coding system based on this model is outlined. The proposed approach is shown to give better performance than transition encoding based on a standard CELP algorithm at rates of 4.8 kb/s