Multimedia network synchronization in real-time applications.

摘要

arious synchronization issues arising in the transfer of voice, video, or data through communication networks for real-time applications are the subject of this thesis. Multimedia communication involves many complex problems that do not appear in other means of communication, such as radio communication. This is because in multimedia communication networks, each type of traffic may travel independently from the other and experiences different network jitter (variation of the delay). This becomes further complicated by the absence of a universal clock.;The multimedia synchronization transport protocol presented in this thesis is divided into three building blocks: (a) Point-to-point single-medium synchronization block, (b) Intermedia synchronization block, and (c) Interparticipant synchronization block.;The proposed multimedia synchronization protocol is based on statistically evaluating the reference times or expected arrival times of the packets from each participant in each connection. Once the reference times are estimated, synchronization is achieved not according to the generation times of the packets but according to their expected arrival times. This approach exhibits the optimum delay, because packets from each connection exhibit the maximum delay seen only in their own connection. Furthermore, deletion/addition of each participant and/or media connection can happen independently to other participants and media connections.;An effort was also devoted in representing the sequence number of each packet with the minimum number of bits. It is proven that the time interval the optimal sequence numbering scheme for multimedia synchronization should span needs not to cover a time duration greater than the maximum of the following two expressions: the maximum variation of the network jitter and twice the maximum absolute difference between the expected time delays of the two media.;Another issue is the frequency offset existing between the sender and the receiver. Knowledge of the frequency offset implies accurate knowledge of the generation period