Signal encoding method and apparatus

摘要

A method and apparatus for encoding an input signal, such as a broad-range speech signal, in which plural decoding operations with different bit rates is enabled for assuring a high encoding bit rate and for minimizing deterioration of the reproduced sound even with a low bit rate. The signal encoding method includes a band-splitting step for splitting an input signal into plurality of bands and a step of encoding signals of the bands in a different manner depending on signal characteristics of the bands. Specifically, a low-range side signal is taken out by a low-pass filter (LPF) 102 from an input signal entering a terminal 101, and analyzed for LPC by an LPC analysis quantization unit 130. After finding the LPC residuals, as short-term prediction residuals by an LPC inverted filter 111, the pitch is found by a pitch analysis circuit 115. Then, pitch residuals are found by long-term prediction by a pitch inverted filter 112. The pitch residuals are processed with MDCT by a modified DCT (MDCT) circuit 113 and vector-quantized by a vector-quantization (VQ) circuit 114. The resulting quantization indices are transmitted along with the pitch lag and the pitch gain. The linear spectral pairs (LSP) are also sent as parameter representing LPC coefficients.