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

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.