Software Design And Implemention Of A Digital Voice Transmission System

The digital voice transmission system introduced in this thesis is a subsystem,which belongs to the indoor and field work integration system researched by our laboratory.However,the indoor and field work integration system is an internal and external industry integrative,real-time,effective,surveying and mapping system.This system sets the global positioning system,remote sensing system,geographic information system,communication system,embedded system and all kinds of custom system as a whole.At the same time,it is equipped with the real-time generating function of real-time satellite positioning,the real-time photogrammetric survey,communication,real-time data processing and surveying and mapping results.This thesis combined with the requirement of the author's laboratory project designed a set of software of digital voice transmission system based on the C/S model and the idea of object-oriented programming.In the course of the design of C-terminal(Client terminal)which can also be called the field-work handheld terminal software,the author uses the double cushioning design scheme for the aim of resolving the discontinuous voice data problem while playing the voice.Such problem can be caused by the reason that the voice data may be unable to carry on continuous compression or decompression when the system operation is busy.Meanwhile,the author also uses the dynamic circular buffer design scheme to alleviate the voice shaking problem based on the strategy of the synchronization of broadcast time to remove jitter,which is due to the time-lag generating during the network transmission process of voice data.Then in the design of S-terminal(Sever terminal)which can also be called the indoor voice data,the author uses the model of IOCP(Input and Output Completion Port).The advantage of using this model can not only assure that indoor voice server can carry higher data concurrency;keep the higher rate of data throughput,but also shorten the development cycle of the server software and reduce the development costs.In the end,the author uses the voice noise reduction technology to optimize the digital voice transmission system,which also improves the speech listening quality.The system of digital voice transmission which is designed by this thesis can provide an actual-time digital communication among the field handheld terminals and between the field handheld terminal and the indoor voice server.In other words,it can be called digital audio broadcasting and digital speech communication.After a series of examination,the system runs well.Consequently,it has reached the basic standard of voice communication which is also the requirement of he indoor and field work integration system.