A New Vocoder based on AMR 7.4kbit/s Mode in Speaker Dependent Coding System

A new code excited linear predictive (CELP) vocoder based on Adaptive Multi Rate (AMR) 7.4 kbit/s mode is proposed in this paper. The proposed vocoder achieves a better compression rate in an environment of Speaker Dependent Coding System (SDSC) and is efficiently used for systems, such as OGM (Outgoing message) and TTS (Text To Speech), that stores the speech data of a particular speaker. In order to enhance the compression rate of a coder, a new Line Spectral Pairs (LSP) codebook is employed by using Centroid Neural Network (CNN) algorithm. Moreover, applying the predicted pulses used in fixed code book searching enhances the quality of synthesis speech. In comparison with original (traditional) AMR 7.4 Kbit/s coder, the new coder shows a superior compression rate and an equivalent quality to AMR coder in term of informal subjective testing Mean Opinion Score(MOS).