Data Transmission. Video Tools And Control Mechanisms

With the requirements and characteristics of Computer-Supported Cooperative Work, this thesis discusses several research results in multimedia communication, which include the transmission for media streams, especially for video streams, and the control mechanism corresponded to video streams. It aims to construct a grouped, low time-delay video tool based on the computer network environment in existence. The main work of this thesis is described as following:(1) Under the analysis of the data transmission architecture of current video tools, a hybrid data transmission is proposed. The architectures of current video tools may be divided into the centralized and the decentralized. The centralized architecture has the shortage of low bandwidth utilization and long time-delay, Although the decentralized architecture based on multicasting utilize the network bandwidth more sufficiently, there exist the lacks of security and reliability and the complexity of management. The hybrid data transmission architecture presented exert the advantages of both the centralized and the decentralized, which have the video tools with both the high transmission efficiency and the system management flexibility and reliability.(2) An network bandwidth allocation and reservation scheme for Ethernet is presented, which is to solve the problem of unable to allocate a fixed bandwidth for real-time video streams because the bus-based network share transmission media and bandwidth resources. In the scheme, the network bandwidth is used sufficiently and the video stream are transmit smoothly in real-time on Ethernet(3) The shortage of bandwidth is the bottleneck for video tool on Internet. The video transmission based on multicast relax the press of the requirement for bandwidth, but in self-adaptive system the feedback messages of status from receiver to sender may generate the implosion of message. We improve the feedback transmission scheme, so that this scheme can decrease or disperse the feedback status messages.