用分数延迟改进基音预测的CELP编码方案

在ＣＥＬＰ编码器中，通常用延迟为抽样间隔整数倍的长项预测器表征浊音语音的准周期性，然而在低比特率，这种限制降低了编码器的性能。本文在介绍了ＣＥＬＰ编码器原理及激励码本构成后，重点研究了一种新型的基音预测方法；分数延迟基音预测，计算机模拟结果表明，这种方法能对浊音进行更准确的表达，尤其对女性讲话者明显改善了语音质量。

Improved Pitch Prediction with Fractional Delays in CELP Coding

The CELP Coder usually uses a long-term predictor that the delay is the integer multiples of sampling interval to exploit the quasi-periodic structure of speech. At low bit rates, this restriction degrades the performance of the coder. The basic principle of CELP coder and construction of excitation codebook are introduced firstly. A new Pitch prediction method with fractional delays is discussed mainly in this paper. The computer simulation results show that this approach enables a more accurate representation of speech and achieves obvious improvement of synthetic quality of speech for female speakers.