Design And Implementation Of SIP-based IP Video Phone

With modern communication technology developping, the video communication which combined data, voice with video transmission became the hot fashion of communication industry. Video Communication had been restricted by the bandwidth of transmission network and the information processing technology. As the broadband network developped rapidly, new video and audio compressed coding standards have more powerful compression capacity, semiconductor manufactor product more and more high-speed digital media processor, from a technical perspective, some kind of quality-assurance communication service can be provided to users.H.323 is an multimedia communication standard based on the IP network without QoS which is defined by ITU-T. Now, H.323 is the main standard for video communication. However, because of the complexity of H.323, it is challenged by SIP, an IP network multimedia communication signing protocol which is defined by the SIP work group of IETF. SIP has good extensibility, and SIP is so simple that it is easy to implement. The prospect of SIP being applied in video communicaton is very fine.The high price of terminals is a very important reason that video communication cannot be a popular communication mode. At first, this paper discussed the key technology of video communication which is based on IP network, such as voice compressed coding and decoding, video compressed coding and decoding, control signaling protocol, realtime data transmission and controlling. And then give an high performance, low price and abudance function design of video communication terminal and some key module implementation.The hardware design is based dual-core, high speed DSP chip—BF561. BF561 had the both advantages of RISC and DSP, so that it can be both the main process and the processor for audio and video process. The software design is based on uClinux operation system, and some porting of open source software such as oSIP, a kind of SIP stack software, and jrtplib, a kind of RTP stack software. The software is design based on scalar framework. The emphases of design and implementation are the porting of uClinux and the optimize of video codec base on BF561's dual-core structure. In this reference design, core B of BF561 is only used to coding and decoding video data, core A of BF561 is act as main processor that handel user's input, network data and something else. Semaphore is used to keep synchronization between core A and core B.All function is implement by software in this design. And the design sufficiently make use of excellent production of open source software. So this design had some advantages such as simple structure, high performance-price-ratio, easy to developing and support new audio, video compressed coding protocol and new functions. The design had good prospect in application to video communication.