| Related technologies of VoIP are introduced, mainly focusing on the G.729speech coding standard. VoIP Voice Gateway is currently the focus of IT communications research and has an important practical significance for the development of communication. The main idea of VoIP is to achieve voice communications on the telephone network and the Internet, i.e., to realize voice calls for circuit-switched telephone network and data exchange Internet network through the VoIP gateway, making mutual networking communication available anywhere. However, there exist many technical issues such as communication bandwidth, delay, error rate for real-time voice communication due to some inherent flaws of the Internet network. It is simultaneously scabrous for signaling initiation, conversion, control of circuit-switched voice communications and data exchange.As many technical issues involved in the VoIP gateway, it is difficult to conduct a comprehensive study in a short time. In this article, VoIP gateway-related technologies are briefly presented, highlighting the G.729speech coding technologies. G.729coding standard is currently a mainstream VoIP gateway coding standards, sampling of8kHz, encoding quantized audio input of the16bit linear PCM, which is a8kbit/s bandwidth telephone speech coding standards. Spectral efficiency is currently an important aspect for communication system, and voice communications is the most important applications at present. Therefore,voice signal of high quality is transmitted with the smallest bandwidth in voice communications. The G.729standard just meets the requirements of low bit rate, high-quality voice communications. However, it requires high computational speed of the hardware to achieve a large number of computing algorithms. Therefore, with no voice quality reduction, it needs to reduce computational complexity as much as possible for G.729voice coding standards, to facilitate the application of the relative economic hardware to implement it. Through the study of G.729standard, the computation of speech coding algorithm is mainly focused on codebook search and the operation of the LP parameters. This article focuses on the study of G.729adaptive codebook and fixed codebook search algorithm and makes improvements, and reduces the computational complexity. under the premise of ensuring the voice quality. At the same time, through the Simulink modeling, it is simulated for the effect of different bit error rate in actual communication on quality of voice communication. Finally, use the DSP of TMS320VC5402to implement G.729, in which process the C code is optimized to reduce the encoding and decoding computational complexity, so as to greatly lessen the DSP computational complexity and storage capacity. The first two chapters of article introduced the development status and prospects of VoIP gateway and related technologies. And the G.729voice coding theory and6.4kbit/s extension are described in Chapter3. Chapter4makes Simulink models of the G.729standard, and simulates different channel bit error. Chapter V simply describes the DSP hardware architecture, advances in G.729algorithm, the C code optimization and DSP implementation. |
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