Code oscillation linear prediction encoder and decoding vessel

摘要

PURPOSE: To provide a code exciting linear prediction coder and a decoder which is hardly affected by quantizing noise for a linear prediction coefficient end improves sound quality even in the case of a low bit rate. CONSTITUTION: The linear prediction coefficient obtained from a locally reproduced synthetic audio signal sequence by a linear prediction analyzing circuit 31 is converted to an LSP parameter by a first parameter converting circuit 32 and impressed to an LSP parameter control circuit 33. The LSP parameter control circuit 33 reduces the influence of quantizing noise and impresses the coefficient to a second parameter converting circuit 34 by linearly adding this LSP parameter and an LSP parameter set in advance while using a coupling coefficient. The inputted LSP parameter is converted to the linear prediction coefficient and impressed to a linear prediction filter circuit 25 by the parameter converting circuit 34. The coupling coefficient is varied based ON norm between adjacent LSP parameters so as to change the rate of adding the LSP parameters set in advance corresponding to the quantity of quantizing noise.