8Kb／s多值脉冲幅度代数码本ACELP语音编码

An 8 Kb/s ACELP Speech Codec with Multi-Level Pulse Amplitude Algebraic Codebook

提出的８Ｋｂ／ｓ语音编码，是采用多值脉冲幅度代数码本的码激励线性预测（ＣＥＬＰ）语音编码技术，基频延迟仅保留整数，代数码本码矢量长度为６４抽样点，具有８个多值非零脉冲．采用快速码本搜索法降低编码复杂性，增益参数与线型频谱对（ＬＳＰ）频率均采用标量量化．解码器中采用基频前置滤波器和频谱后置滤波器，以提高再生语音的质量．

An 8 Kb/s speech codec is proposed. The encoding algorithm is based on Code-Excited Linear Prediction (CELP) with a multi-level pulse amplitude Algebraic Codebook (ACELP). Only integer pitch delay is searched. There are & non-zero pulses with fixed amplitudes, each of + l, or +0.5,or -1 or -0.5, in each algebraic codevector of length 64 samples. An efficient nonexhaustive codebook search method is developed.The codevector's gain and LSP frequencies are scalarly quantized. A pitch prefilter before LP synthesis filter and a spectral postfilter after LP synthesis filter are adopted in speech decoder to enhance the reconstructed speech quality.