Research On Audio And Video-based Bus Scheduling Terminal Under The 3G Network

This dissertation mainly presents key technologies of audio and video transmission under the 3G network. Besides it presents the development of VoIP voice intercom and video surveillance and combines with the actual situation of public transport to develop audio and video-based bus scheduling terminal system under the 3G network.develop public transport and improve the level of public traffic information is the key to optimize public transport operations. The core of transportation industry management is operations and safety of the public bus, and the level of dispatching is a direct impact on the business income and the quality of service to passengers. Because "Large number of casualties"event increases, more and more protection of taking bus is concerned by all levels of the society. Because of the increase of development of GPRS business, public transport enterprises have built information platform based on the 2G network to achieve the monitoring of transit vehicle location and a limited schedule of the vehicle based on the "SMS" model. With the developing of 3G technology, it is great significant to achieve a "find", "visible", "hear", and "turned up action" scheduling system.VoIP voice intercom function modules mainly include:real-time speaking, team calls, group calls, and voice monitoring function of the scheduling, which not only can ensure efficient scheduling operations, but also can provide protections for emergency treatment. Video monitoring module mainly contains:video interaction and scheduling, real-time passenger information control, real-time monitoring the alarming vehicle, and inquiring historical video information. The main work of this dissertation is adopting linux operation system to complete software development based on the existing hardware platform. The subject did not cover the very mature conventional scheduling but focused on the two modules of VoIP voice intercom and video monitoring and dispatching. Video monitoring under the wired network and technology of VoIP phone has been matured already, but the signal stability of 3G wireless networks, transmission delay and other aspects can not be as good as the wired. There are restrictions in coverage area, cell switching, and the number of channels of 3G network. Therefore, the main topics of research are:analysis of the 3G wireless networks features, analysis of the key factors of wireless bandwidth and the delay of each link, and researches on module selection, encoding and decoding programs, real-time detection of wireless network bandwidth, the package of voice and video streams, transmission protocol stack, and frame dropping stream of technology. Finally a controllable time delay, high utilization of network bandwidth wireless network transmission technology is achieved.The main features of the system are:difference between audio and video streaming and control signaling channel, simultaneous collection of network status information at the receiver and transmitter, UDP bulk for a replacement in transfer process, the sliding buffer window, discarding all the frames when there exising missing frames in a GOP, and uniform fast transmission of little packets. Through these measures we can overcome the defects of fluctuation of the wireless network bandwidth, packet loss and bit error rate, and guarantee quality and smooth of video images, the balance of the short time delay protection of voice calls, voice fresh and meet the need of the scheduling bus VoIP voice intercom, video surveillance of the "visual", "face to face ".The research results have already been applied in bus scheduling system successfully. The public transportation scheduling level is improved and the bus companies investment of resources is reduced. Passenger's waiting time is reduced, and the traffic management level is improved. The loss of fare, non-standard traffic and other problems are resolved. The security of bus is guaranteed, and the scene of major events can be decision-made and commanded, which deterrents and combats theft, arson and other crimes effectively.