Personal speech coding

In existing speech coding systems, all quantizer codebooks are designed to suit the statistical and perceptual characteristics of speech signals of a population of speakers. However, an individual’s speech signal does not exhibit, even over a long time, the entire range of characteristics of the population. With the advent of the personal communication systems, personal information might become available and be used to improve the rate-distortion performance of speech coders. In this paper we assess the potential gain of personal speech coding by designing codebooks for individual speakers. Spectral quantization, excitation and pitch lag codebooks of existing CELP coders are redesigned. The gains appear to be modest, suggesting that we need to use a different coding framework, which can model personal characteristics explicitly. Amongst the components, the spectral quantiser seems to be most amenable to personalisation.