Research On The Key Technologies Of Adaptive Low Bit Rate Speech Coding

Speech coding is one of the hotspots in modern multimedia communications. So far, there have been several classical coding methods. To meet the requirement of some particular fields, especially wireless communication, benthic communication, military communication, satellite communication, secrecy communication and voice storage, the demand for low bit rates speech coder will increase rapidly in the very near future. The pressing problem is to guarantee a well speech quality at extremely low bit rate.This paper mainly focuses on the research and improvement of the fast code word search algorithm, speech enhancement and voice activity detector key technologies. A high robust improved harmonic vector excitation LPC speech coder is proposed by using the improved key algorithm and multi-frame joint vector quantification principle. The experiment results show that the informal subjective speech quality of the improved speech coder at 1.1kbps is better than that of FS1016 4.8kbps CELP, which performs as well as the 2.0kpbs HVXC. In addition, owing to the adoption of the fast code word search algorithm, the improved speech coder overcomes the shortcoming of the long time-delay and performs efficiently in real time speech communication, which makes a foundation for the deeper research.