The Implementation And Research Of Real-Time Voice Transmission Based On RTP

VoIP is a technology that mostly utilized in IP phone, and relevant value-added services. The most advantage of VoIP is that can make use of the global IP internetworking environment, to provide the more and more,the better and better services than tradition PSTN network. The IP phone using VoIP technology is the result of the combination of such chief technology, the packet technology on network taking IP as its sign, and the integrating technique of services on network taking real-time media transmission as its goal. It has become the joint of traditional telecom and IP network, mutually supplying each other's advantages.Due to the intrinsic character of IP network, it maybe be competent for transmission discrete media such as text,picture etc, but it is insufficient to transmit real-time media such as audio,video and so on. How to transmit real-time media with high performance over IP network that has become the most important problem in VoIP field.Under such a background, as a part of the research work on VoIP gateway, the author carried through the real-time voice transmission deeply, and bring forward some measures to improve voice quality on delay,jitter,packet lost aspects, then realize the multicast audio meeting.This article first introduced some background knowledge including voice encoder/decoder,signaling technology,stream media protocol. And then gave an exhaustive description on RTP/RTCP protocol, analyze the protocol using scenarios. Afterward provided a real-time voice transmission resolution upon embedded Linux. This resolution adopted multiple ring buffer and multi-thread technology to implement multicast audio meeting based on RTP/RTCP, supply resolved means on multiple voice synchronization; decrease the network voice jitter through the de-jitter buffer algorithm, and try to find the trade-off between the voice delay and jitter; At the last of article, the author provided the test results about real-time voice transmission bandwidth,delay, put forward some perspective views tailor to problems which exists on large-scale RTP/RTCP application scenery.