VoIP Implementation Technology Research Based On Television Box

VoIP is packetized digital media transmission technology based on IP technology,due to its effective use of advantages of Internet IP packet switching technology,compared with traditional PSTN network, it can significantly reduce the communicationcost, improve communication line utilization, and can easily achieve new business. Inrecent years, VoIP technology has been developed rapidly and becomes a hot spot in thefield of Internet application.VoIP system is based on signaling protocols, H.323and SIP protocols developed byITU-T and IETF have become two mainstream signaling protocols. Compared with H.323,SIP has the following advantages: SIP uses the form of text, so its structure is simple andflexible, convenient for debugging and expansion,more in line with the VoIP technologytrends in the NGN environment. Therefore, a SIP stack based on the model of SIPtransaction state machine is the key research point, it solves SIP signaling parsing andcontrolling problems. A SIP stack wrapper is implemented on the SIP stack to make thecontrolling of main SIP signaling easier by upper modules.In order to achieve the functionality of processing media data, a media sessionmodule is designed and implemented. Main work of media session module is real-timemedia transmission sub-module to complete the underlying RTP media data transmissionfunction, jitter buffer designed to solve the jitter of the media data and the designation ofmedia data processing flow management mechanism to facilitate the processing of mediadata functionality extension.In order to solve the affection of NAT, a SIP NAT traversal scheme, which is acombination of STUN and TURN, is designed, and NAT traversal module used by clientis implemented.