【作者】 张峰；

【导师】 汪蕙；

【作者基本信息】 清华大学 ， 电子科学与技术， 2009， 硕士

【摘要】 随着数字技术的不断发展,电子信息领域的各种传统的模拟技术均开始了数字化进程。在广播领域,DRM(Digital Radio Mondial,数字无线电联盟)作为一种针对30MHz以下的长、中、短波波段的数字广播标准也应运而生。DRM系统采用了先进的信道和信源编码技术,使得在AM(Amplitude Modulation,幅度调制)波段的音频质量大大提高。首先,本论文对DRM系统的信源编码技术进行了研究,DRM系统的信源编码采用了MPEG-4 AAC(Advanced Audio Coding,高级音频编码)编码标准的一个子集,并采用了SBR(Spectral Band Replication,频带复制)和PS(Parametric Stereo,参数立体声)两种音频编码技术,使得编码码率能大大压缩。本论文主要研究DRM系统中的SBR和PS技术的实现,以及两种技术的使用对DRM系统编码性能的影响。在SBR和PS技术使用之后,编码性能相比未使用前均提高了33%以上。其次,本论文研究了两种DRM系统中的信息隐藏方法。一种是基于比例因子量化的信息隐藏方法,主要运用DRM信源音频编码技术中的比例因子量化提供的冗余来进行信息隐藏;另一种是基于Huffman编码的信息隐藏方法,主要运用DRM信源音频编码技术中Huffman编码中的码对替换来进行信息隐藏。本论文分别对两种信息隐藏方法的稳定性、隐蔽性和嵌入量进行了研究。基于比例因子量化的信息隐藏方法在嵌入量上基本不受限制,在稳定性和隐蔽性上也处于很好的水平,缺陷是信息嵌入后会较显著改变生成音频文件的大小。基于Huffman编码的信息隐藏方法的嵌入量较小,只有不到原始音频文件大小的0.02%,且在数据嵌入较多时在隐蔽性上表现也不够理想,但是其信息嵌入后不改变生成音频文件的大小。最后,本论文总结了所有的工作,并对于两种信息隐藏方法的联合使用做出了展望,对下一步的工作指出了方向。更多还原

【Abstract】 With the development of digital technology, digital technology begins to replace anologue techonology in IT domain. In broadcasting domain, DRM is a new digital broadcasting standard which is used for Long-, Medium- and Short-Wave Bands below 30MHz. Advanced channel coding and source coding technologies are used in DRM system, which improve the audio quality a lot in AM band.Firstly, we did some research on sorce coding technology of DRM system. A subset of MPEG-4 AAC coding standard is adopted in DRM system. SBR and PS technologies are also adopted in order to reduce the coding bit rates. We researched and developed SBR and PS techonoly, and we also evaluated how SBR and ps influence coding performance of DRM system.Secondly, we researched and developed two information hiding method in DRM system. One is based on scale factor quantization which use the redundancy provided by scale factor quantization to hide information, and the other is based on Huffman coding which use Huffman code to hide information. And we evaluated transparency, robustness and capacity of these two methods. The information hiding method based on scale factor quantization has almost unlimited capacity. It is also good at transparency and robustness. But the size of the audio file will be changed when information is hided. The information hiding method based on Huffman coding has a small capacity which is less than 0.02% of the original audio file. And its transparency is not good when more information is hided, but it wo’nt change the he size of the audio file when information is hided.Finally, we summarize our work and propose a combination method of two information hiding method.更多还原