基于H.323协议的独立IP可视电话的设计与实现  

The Design and Implementation of Standalone IP Videophone Based on the H.323 Protocol

作　　者：方湘艳[1] 朱荣[1] 李红[1] 段汉文[1] 

机构地区：[1]武汉大学多媒体网络通信工程湖北省重点实验室,武汉市珞喻路129号430079

出　　处：《武汉大学学报（信息科学版）》2002年第1期89-93,共5页Geomatics and Information Science of Wuhan University

摘　　要：论述了独立IP可视电话实现的关键技术 ,介绍了H .32 3协议的相关内容 ,并在H .32 3协议框架的基础上提出了一种可行的独立IP可视电话的设计和实现方案。This paper analyses the future development of the standalone IP videophone and its excellence in comparison with tradition videophone,expatiates on the application of the standalone IP videophone and introduces the structure of H.323 system and some protocols which include video code,audio code,system control(H.245 control,H.225 call control and RAS control) and H.225 layer. This paper puts forward a project of standalone IP videophone with the frame of H.323 protocol which includes two parts,hardware and software. The hardware part mostly consists of CUP processor,video processor,audio processor.CPU processor is made up of RA_RISC,ROM and SDRAM and employs W90221 chip,W9961 chip and W9975 chip.W90221 is connected with network processor and video processor by PCI bus and with audio processor by synchronization series interface(SSI).W9961 chip compresses and decompresses video signals,which is based on standard ITU_T H.261 and H.263 protocols and can work with 32_bit RISC Processor.W9975 chip can apply the videophone with H.323 or H.324 system and IP videophone with IP network. The software part mostly includes drivers and applications.The drivers are used to manage the hardware resources and serve the applications as library.the drivers are made up of audio_base,Video_base,interface_base,TCP/IP protocol_stack and H.323 protocol_stack.The applications include seven tasks:H.323 main task,net task,user input task,monitor task,message dispatcher task,G723 transmit task and H.263 transmit task.They achieve the operations of communication,synchronization,mutex through message queens,event,signal lamp,and finish the system functions unanimously.The project imports embedded operation system Super_Task to manage and control the system resources.

关 键 词：H.323协议 IP可视电话 音频编解码 视频编解码 嵌入式操作系统 多任务 

分 类 号：TN949.28[电子电信—信号与信息处理] TP393[电子电信—信息与通信工程]