【作者】 张颖；

【导师】 万旺根；

【作者基本信息】 上海大学 ， 电子与通信工程（专业学位）， 2015， 硕士

【摘要】 随着数字化语音通信的蓬勃发展,越来越多的模拟话音系统开始升级成数字通信设备。鉴于现在的网络带宽条件所限,语音信号在送到通信线路前,一般要进行压缩处理以节约信道资源。中低速率语音编码器G.723.1协议由于码率较低、语音质量好、支持双速率编码等优点非常适合于数字通信中的语音编码传输,在语音通信系统中得到大规模应用,所以本课题选用G.723.1作为压缩算法。由于G.723.1较高的运算复杂度,在构建实时音频压缩系统时,需要使用高速的DSP处理芯片。本课题采用TI公司最近推出的高性能DSP芯片TMS320C6748实现了基于DSP的实时语音压缩编解码系统。主要工作包括以下四个方面:G.723.1算法的移植和优化,系统的软件设计与实现,系统的硬件设计,系统语音质量的主观与客观测评。本文首先深入的研究了G.723.1算法编解码原理,在算法优化方面,运用了DSP内部指令集以及内存优化等多种方法大幅降低算法运行耗时,达到了语音编解码实时性要求。在音频数据采集方面,设计了EDMA乒乓传输模式,从而实现了音频数据的连续后台传输,有效的减少了CPU负荷。此外在串口通信方面编写了串口驱动程序并设计了通信数据帧格式,实现了稳定的G.723.1数据全双工串口通信。最后对整个系统进行语音质量的主观与客观测评,证实系统运行良好并达到设计要求。更多还原

【Abstract】 With the development of the digital speech communication, more and more analog speech systems began to upgrade into digital communication device. Because the very limited bandwidth, the digital speech data on the channel must be compacted. Due to the G.723.l codec algorithm has a lower bit rate and good reconstruction speech quality, it is very suitable for multimedia communications in speech coding transmission. In view of the G.723.1 codec algorithm has a high time complexity, the operational ability of DSP must be strong, so we use TMS320C6748 DSP chip as the core.In this paper, the real-time G.723.l speech compression system use TI(Texas Instrument) High-Performance TMS320C6748 DSP chip as the core. The main work includes the following four aspects: The transplantation and optimization of G. 723.1algorithm, the system hardware design and implementation, the system software design and implementation and the evaluation of system voice quality.At first, this paper deeply study the G.723.1 codec algorithm theory. In terms of algorithm optimization, using the DSP internal instruction set and memory optimization methods greatly reduce algorithm running time. In terms of audio data collection, designing the EDMA ping-pong transfer mode, so as to realize the continuous background audio data transmission, effectively reduce the CPU load.Besides, writing serial port driver and designing the communication data frame format, realize the stable G. 723.1 full-duplex communication. At last, it is proved that the real-time speech compression and transmission system is achieved by testing the real-time full duplex system.更多还原