| 摘要 |
PURPOSE:To allow extremely efficient quantization and to provide the voice coding system which is good in sound quality even at a low bit rate by subjecting the spectral parameter of a voice signal to a nonlinear transformation corresponding to the characteristic of hearing sensation to make vector quantization. CONSTITUTION:An LPC analysis circuit 130, an LSP quantization circuit 140, an impulse response calculating circuit 170, a weighting circuit 200, and adaptive code book 210, a sound source code book retrieval circuit 230, a sound source code book 235, etc. are provided and the spectral parameter is determined by approximating the inputted discrete input signal by an all Polar type model. The frame is divided to small sections and the pitch parameter is so determined that the signal reproduced in accordance with the past sound source signal is approximated to the voice signal. The spectral parameter is subjected to the nonlinear transformed so as to correspond to the characteristic of hearing sensation by the voice coding system which outputs the sound source signal of the voice signal by expressing the same by the code book. This parameter is expressed by the previously constituted code book 210 and is outputted. The voice coding system which is good in sound quality at <=4.8kb/s is obtd. by the relatively small computation quantity and memory quantity in this way. |
