中文摘要：

针对VoIP系统普遍使用G.729a语音编码,采用逐帧按位取反的方式对G.729a语音进行全面测试,以客观的语音质量感知评价（PESQ）标准为依据,总结G.729a语音帧中可隐藏位（最低有效位）.结合矩阵编码算法,提出一种基于G.729a语音的信息隐藏方法,以大量的语音样本为载体,对该方法进行测试分析.实验结果表明：该方法能提供可观的隐藏容量（8bit·帧-1）,较高的嵌入效率（2.678）,很好的不可感知性（平均PESQ值为3.593）,且很好地符合了VoIP通信的实时性要求.

英文摘要：

For G. 729a speech codec widely used in VoIP systems, a one-by-one bit flipping test for G. 729a speech is car- ried out, and the available bits for steganography （least significant bits） are correspondingly obtained based on perceptual evaluation of speech quality. To combine with matrix encoding, an information hiding approach based on G. 729a speech is proposed. The approach is tested and evaluated with a large number of speech samples as the carriers. Experimental re- suits demonstrate that the proposed approach can provide a relatively high hiding capacity （8 bits/frame）, higher embed- ding efficiency （2. 678）, good imperceptibility （the average PESQ score is 3. 593） and nice real-time performance that meets the requirement of VolP systems well.