【作者】 刘兴旺；

【导师】 张雪英；

【作者基本信息】 太原理工大学 ， 电路与系统， 2010， 硕士

【摘要】 在现代的通信系统中,在GSM和WCDMA系统中使用的自适应多速率编解码器是一种多速率的窄带编解码器,然而随着数字通信网络的飞速发展和视听业务需求量的日益增长以及人们追求一种自然的面对面的通信质量和带宽的限制越来越不适应人们对高质量语音业务的需求,为此,有必要进行宽带语音压缩编码的研究。为了满足对高质量语音业务的需求,3GPP/ETSI提出了宽带自适应多速率编解码器。随后,AMR-WB又被ITU-T选用为其16kbit/s宽带语音编码标准G.722.2。自适应多速率宽带语音编解码器由于其音频带宽扩展到7kHz,采样频率扩大到16kHz,突破了窄带语音编解码器带宽方面的限制,因此在语音的自然度、音乐处理等方面有较大的改善。AMR-WB具有语音质量高、平均编码速率低和自适应好等优点,是通信史上第一种可以同时用于无线与有线业务的语音编码系统,在无线和有线通讯领域都有着广阔的应用前景。本文对AMR-WB算法进行了系统的分析,深入研究了编码器的矢量量化、自适应码本搜索和固定码本搜索等几个模块并对其相应的算法进行了优化,还对解码器的解码原理进行了一定程度的分析和研究。选用TIMIT标准英文语音数据库中的标准语音文件(16kHz,16bit)进行编解码实验,对编解码后的语音质量进行了主观听觉测试和客观w-PESQ测试,测试结果表明12.65kbit/s以上模式,合成语音的波形与原始语音基本一致,在听觉上已经与原始语音难以分辨,w-PESQ值都超过了4.0,而对于6.60kbit/s和8.85kbit/s模式,在波形和听觉上稍有失真,w-PESQ值都在3.5以上,达到了通信质量标准,而且合成语音具有良好的自然度和听觉舒适性。本文对宽带语音编码标准G.722.2 (AMR-WB)进行了矢量量化的改进实现,自适应码书搜索的改进实现和代数码书搜索的改进实现。并且对各种改进的算法分别进行了编解码测试,对其语音质量进行了评测,并与原始的宽带语音编码标准G.722.2算法相比较,对于矢量量化的改进和自适应码书搜索的改进而言,两者都可显著降低码书搜索的计算复杂度,语音编码算法的时间得到显著降低,改进的快速码字搜索算法都是实现快速编码的有效方法,具有一定的应用价值。代数码书搜索的改进算法与原始代数码书搜索算法相比较,改进的代数码书搜索算法可提高标准算法语音质量,具有一定的参考价值。更多还原

【Abstract】 In the public telephone networks, The AMR(Adaptive Multi-rate, AMR)speech codec used in GSM and WCDMA system is a multirate narrowband speech codec. For the limited bandwidth, the narrowband AMR speech codec can’t satisfy people’s needs to high quality speech services. With the rapid development of the digital networks and audio-visual technique application, people are in the pursuit of face-to-face communication. Conclusively the research of the wideband code is necessary.In order to meet the requirement in high quality speech services, 3GPP/ETSI proposed the adaptive multi-rate wideband speech codec.After that, the AMR-WB codec was selected by ITU-T in the standardization activity for wideband speech coding around 16kbit/s. AMR-WB(Adaptive Multi-rate Wideband, AMR-WB) codec makes speech frequency extended to 7kHz and sample frequency extended to 16kHz, greatly breakthroughs the restriction of the bandwidth than the narrow band codec. Therefore, AMR-WB codec will ameliorate greatly in many aspects such as speech naturalness and musical processing. AMR-WB has the advantages of high speech quality, low average bit rate and strong adaptability. The adoption of AMR-WB by ITU-T is of significant importance for it is the speech code system adopted both by wireless and wire line service at first time, and will be used widely in wireless communication fields as well as wire line communication fields.This paper systemically analyzed the AMR-WB algorithm. Based on deep research of vector quantization, adaptive codebook search,fixed codebook search, high band process and the decoding principle, the AMR-WB algorithm was simulated. The standard speech files(16kHz,16bit) of TIMIT standard English speech database were selected to accomplish coding and decoding experiments, then tested the synthesized speech in subject auditory quality and object w-PESQ value. The result showed above the model of 12.65kbit/s, the waveform of synthesized speech is the same as that of input speech, and it had hardly to differentiate with original input speech in auditory, he w-PESQ values were more than 4.0. In the model of 6.60kbit/s and 8.85kbit/s, there were a little distortion in terms of waveform and auditory, and the w-PESQ values were above 3.5. They all reached the communication quality standard and the synthesized speech had the good naturalness and comfortable auditory property.For adaptive multi-rate wideband speech codec algorithm, the paper optimizaties vector quantization and the adaptive codebook search the adaptive codebook search and fixed book search. And improved algorithms encoding and decoding were tested by voice quality algorithm. Compared with the original wideband speech coding standard G.722.2(AMR-WB)algorithm, optimizated vector quantization algorithm and adaptive codebook search algorithm both can significantly reduce the computational complexity and speech coding time, so two kinds of codeword search algorithm is fast and effective coding method and has certain application value. Compared with original fixed book search algorithm, optimizated fixed book search algorithm can improve voice quality and has a certain reference value.更多还原