ACOUSTIC SIGNAL TRANSFORMATION ENCODING METHOD AND DECODING METHOD

摘要

PURPOSE:To perform encodings with small information by flatening efficiently the frequency characteristic of an input acoustic signal. CONSTITUTION:The spectrum characteristic of the input acoustic signal is calculated by executing the modified discrete cosine transformation of the input acoustic signal. On the other hand, a prediction coefficient is calculated from the input acoustic signal in a linear prediction analyzing part 17 and an approximate form of the spectrum characteristic of the acoustic signal is calculated by executing the Fourier transformation of the prediction coefficient in a spectrum approximate form calculating part 21 and a residual coefficient is obtained by normalizing the spectrum characteristic with the approximate form in a normalization part 22. A residual approximate form normalizing part 26 obtains a fine structure coefficient by normalizing the residual coefficient with a residual approximatic form predicted in a residual approximate form calculating part 23 and then a quantization part 25 quantizes vectorially the fine structure coefficient. A reverse normalizing circuit 31 reproduces the residual coefficient by deformalizing a quantized fine structure and the residual approximate form calculating part 23 predicts the approximate form of the residual coefficient of a remaining next frame from the reproduced residual coefficient.