| This subject is from an IP-based voice communication project. It aims to analyz protocals related to VOIP, look for the special implementation methods, and develop an IP-based voice communication software with full source codes. Self-realization of the software can improve the reliability, security and scalability, and meet the specific needs of voice communication.VOIP (Voice over IP) is a kind of voice transporting technology that based on the IP network, mainly including soft switching, real-time transporting, media processing, NAT traversalling and voice security technologies. It has such benefits as less bandwidth, low running costs, good flexibility, and system openning. Its development is vast, and is easy to integrate the latest technologies.This paper analyzes the SIP session control protocol in soft switching technology, the RTP/RTCP protocol in real-time transporting technology, the G.729a voice compression codec protocol and sound card's capturing and playing methods in media processing technology, and the latest P2P technology. SIP session control protocol is easy to use, and has good expansibility, adaptability, and can be combined with the latest P2P technology. RTP/RTCP real-time transporting protocol is complete and mature. G.729a voice compression codec protocol has less bandwidth taking, small coding delay, and good sound quality. Sound card is used in general, and is easily designed to capture and play sounds.The paper also gives the specific implementation of SIP, RTP/RTCP, G.729a and audio programming. Using available opening source codes which selected by comparing and altered for fitting, integrating a variety of developing libraries, secondary programming these different parts for comprehensive utilization of effective organization, a multi-channel VOIP voice communications software was developed. The software has capabilities of session controlling, real-time transporting, voice compressing and codecing, audio capturing and playing, and multi-channel working. |
PDF Full Text Request