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The Design and Implementation of VoIP Calling Protocol Analysis and Voice Data Decoding

Author: YuCong
Tutor: ShenBeiJun；ZhuGang
School: Shanghai Jiaotong University
Course: Software Engineering
Keywords: Protocol analysis Voice and data decoding H.323 protocol stack VoIP Monitoring
CLC: TN916.2
Type: Master's thesis
Year: 2008
Downloads: 44
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Abstract

With the rapid development of data communications technology, TCP / IP protocol has become dominant and dominant network technology, on the basis of the IP network to provide various types of services has become an important trend for the development of communication network technology. VoIP (Voice over IP), also known as IP telephony, is an important service in IP networks. Any new technology is a double-edged sword, the rapid development of the IP phone to bring affordable, convenient to the people living at the same time, certain criminal activities has also become a new communication contact to the public security work, this proposed new challenges, the traditional means of monitoring can not do anything. In this situation, the public security authorities new tools are needed to VoIP monitoring. Monitoring of IP telephony is a large project, the most critical call signaling information parsing and decoding technology of voice data, proposed a set of signaling and voice reproduction methods and processes, and The design and implementation of VoIP monitoring system, to effectively restore the original packet from the IP telephone communication, then a single, and voice data. Firstly, in-depth analysis of China's major infrastructure operators when building a VoIP private network using the standard H.323 protocol stack, in particular, and issues related to the core protocol H.225.0 call control signaling and H.245 system control signaling; Then focus on the call flow and voice data decoding technology based on H.323 protocol stack, VoIP the call protocol analysis and voice data decoding restore the overall process; standard access authorization process up a VoIP network for China Unicom authentication information resulting from modifications \The voice decoder draws in part on the ITU standard voice codec algorithms, in order to reduce the complexity of the algorithm, the program moderately modified directly voice and data decoding for IP surveillance system, and raised voice and call information associated methods to achieve complete reduction of the voice. Finally, on the basis of the above key technical research, we have developed a \The system is collected by spectrophotometric China Unicom IP private network data, detailed analysis of the raw data stream from which to restore the information needed by the public security organs to achieve effective monitoring Unicom IP network data. System for communication, then all of the net single and authentication information can be set according to the user selectively intercepted call content of a particular object, and recording playback, support G.723.1, G.729, and other commonly used IP telephony voice decoding special real-time listener channel listener delay of less than 200ms. The practice shows that the system fill the blank of China's public security organs VoIP phone monitoring, to improve the efficiency of case handling reconnaissance.

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