| The paper includes two parts as follow:Description model for multimedia data-flow and Transmission method of multimedia data. In this paper audio and video are the mainly research objects to achieve the two parts.Compared with the traditional data, the most notable features of multimedia data are the spatial and temporal as well as the diversity for description. The description for multimedia data-flow is a structured integration. Each object must have one or more time intervals. In multimedia technology-intensive areas, how to describe the multimedia data-flow is a very prominent problem. The key is how to describe multimedia data-flow.The paper describes methods for time and space coordinates determine of every media object, and then we made a description for multimedia data-flow model. Algorithm has two steps:First, determine the coordinates of each type of media time and space location, and then determine whether to switch to a media.The paper uses SMIL (Synchronized Multimedia Integration Language) to describe multimedia data-flow.As a key technology in multimedia communications, technology of media data collection, compression code and network transmission has been relative mature, multimedia synchronous transfer has become a hot research issue. This paper will deal with the control of audio and video synchronization in both sender and receiver.In order to achieve multimedia data synchronization, the paper has made compare with several synchronization methods, and then brings forward the design of multimedia data synchronization:combination with feedback control mechanism to achieve synchronization based on time-stamp synchronization scheme without synchronous clock of whole power. Synchronous design is divided into two parts:the transmitter and the receiver. Between them, the sender part is composed of data collection, data-flow rate control and time-stamp's disposal.the receiver part is composed of three modules:getting rid of jitter, buffer design, feedback detection design. After testing, the realization of synchronous design is acceptable.The design is based on the relative time-stamp approach. All the multimedia units are put on an interrelated time scale, and the position of media units determine the interrelate time-stamp, and then the media units which have the same time-stamp will be displayed at the same time to achieve inter-media synchronization. This scheme just guarantees the time-stamp relative synchronization between audio and video frame and dispenses with complex means getting exact time value corresponding to time-stamp, so it reduces the complexity of getting time synchronization message and the difficulty of maintaining public time axis. In the receiver, when to play audio is primary media and video is subsidiary media, by comparing to the time-stamps of audio and video frames and throwing away or repeating playing one certain video frame to achieve inter-media synchronization. Furthermore, the paper implements the function of self-feedback-regulation, so it can avoid the phenomena of unable guaranteeing the quality of playing, such as velocity is sent or played so fast or low that the burden of system would be over weight even congestion result as data lost.Design and implementation of multimedia synchronization is the emphatic and difficult part in this paper. |
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