【作者】 张海波；

【导师】 马鸿飞；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2008， 硕士

【摘要】 高质量低码率的压缩技术一直语音和音频编码孜孜以求的目标。语音编码技术可以达到非常低的编码速率,但只能处理窄带语音信号。而音频编码技术虽然可以达到很好的音质效果,但是很难进一步提高压缩比。因此,语音和音频编码技术都在寻找新的技术来实现高质量低码率。频带扩展技术就是一种很好的解决方案。本文回顾了频带扩展技术的主要实现算法,包括非盲式和盲式频带扩展,并把最著名的一种频带扩展实现技术——频带复制技术作为一个独立研究单元,进行深入研究。在本文的结构安排上,首先对实现频带扩展的一些关键技术进行了介绍,并且从EAAC+编解码器中分离出独立的频带复制算法,作为进一步研究的平台。然后,通过对频带复制算法进行测试和评估,发现了频带复制算法的一些不足之处。接着,以频带复制算法为基础,针对其算法存在的缺点,设计出相应的改善策略和解决方法,进而形成一套新颖且完整的频带扩展改进方案,并完成相关测试评估。通过评估,这套新颖的改进方案体现出自身的优点,并在频带扩展的某些方面有明显的改善。虽然改进方案尚不能解决所有的问题,但其改进思想的潜在价值却不容忽视,对其进行进一步发掘和研究相信会很有意义。更多还原

【Abstract】 High quality and low bit-rate has been the targets of both speech coding and audio coding. Speech coding offers very low bit-rate, but it focuses on narrow band speech signals. On the other hand, audio coding provides excellent quality, but it is hard to improve compression ratio. Therefore, both of them are searching for novel technology to help them realize the targets.Spectral band extension (SBE) technology is a good solution for the targets mentioned above. This paper reviews some algorithms of spectral band extension technology, including both non-blinding and blinding extensions, and spectral band replication (SBR). One of the most popular methods of spectral band extension is thoroughly studded. Firstly in the thesis, some key technologies related to SBE are described, a set of algorithms about SBR in EAAC+ software are studded. Secondly, based on tests and evaluations of the algorithms, some of the deficiencies of the SBR processing are addressed. Then some new strategies, methods and algorithms of the SBE technology, which will overcome the drawbacks, are designed and tested.The performances of the innovation schemes have shown some improvements and advantages for spectral band extensions. Even they are not always good in any cases, but still have some potential feathers, so further study and investigations about these issues are expected.更多还原