8 kbit/s 短延时语音编码算法——LD-ACELP

Algorithm of 8 kbit/s low delay speech coding——LD ACELP

８ｋｂｉｔ／ｓ短延时语音编码算法ＬＤ－ＡＣＥＬＰ，采用了代数码本激励线性预测（ＡＣＥＬＰ）的编码方法，利用语音的帧间相关性对线谱对参数采用了分裂式矢量量化技术，并采用高效的码本结构、码本搜索技术和增益矢量量化技术来获得较高的语音合成质量和较短的算法延时。ＬＤ－ＡＣＥＬＰ的帧长为１０ｍｓ，算法延时为１５ｍｓ。通过信噪比及人耳主观听觉实验等性能测试表明，该算法具有与国际电联１６ｋｂ／ｓ短延时语音编码算法ＬＤ－ＣＥＬＰ（Ｇ．７２８）相当的语音合成质量。

In order to satisfy the demands of speech quality and algorithm delay of speech coding algorithm in the digital voice communication system, we have studied a kind of speech coding algorithm with high quality and low delay at the bit rate of 8 kbit/s. The encoding algorithm is based on algebraic code excited linear prediction (ACELP). LSP quantization with split vector quantization (Split VQ) technique using interframe correlation, efficient codebook structure and codebook search strategies, along with efficient gain vector quantization procedures, have been developed to achieve high quality reconstructed speech and low algorithm delay. The frame length of LD ACELP is 10 ms and the algorithm delay is 15 ms. Through performance tests of SNR and subjective listening, we have verified that the proposed algorithm is mostly equivalent to the 16 kbit/s low delay speech coding algorithm LD CELP (Speech coding standard G.728 of ITU).