When the server receives RTSP to request, it first produces the RTSP request object. Server content which will request through the RTSP agreement's response message by class conversation (streaming session) the formal description, the content contains how many class, the media type including the data stream, and arranges the decoding form. A class conversation is composed of or many data streams, like video frequency class and audio frequency class and so on. The actual data stream transmits the client side through the RTP agreement. RTP works in one-to-one or the one-to-many transmission situation, its goal is supplies the time information and realizes the class synchronization. RTP itself cannot provide the reliable transmission mechanism for the smooth transmission data packet, it depends upon RTCP to provide the flow control and the congestion control service together. In RTP conversation period, each connection surveillance lower level network's performance, and will be related the information to put in the RTCP package, periodically transmits the RTCP package to inform the transmitting end. The transmitting end may also use the RTCP package to provide the conversation information each time, in the package includes already the data packet quantity which, loss data packet transmits statistical data and so on quantity. Therefore, the server may use these information dynamic to change the transmission speed, even changes the payload type. RTP and RTCP coordination use, because the effective feedback and the smallest expenses cause the transmission efficiency optimization.
Flows media server's function diagram as shown in Figure 2.
2.3 highly effective class media server's design
Passes the overflow media server's agreement stack's design, may be clear about the class media server is in the transmission level agreement (TCP, UDP) on explained that the RTP, RTCP, RTSP agreement, all customer connection request is obtains by the TCP port, flows the media data also makes into the RTP package, sends through the UDP port, therefore, how as well as to transmit regarding the TCP, UDP port event's dispatch the massive class media data from the floppy disk space to the network in becomes the restriction class media server performance the primary factor.
Flows the media server facing a sole customer, completes the process is as follows:
1) after the client side sends out the RTSP connection request, the server through to the TCP port's monitor, the read-in requested.
2) analyzes the request content, calls in the corresponding class media file.
3) forms the RTP package, the distribution data stream package, obtains the RTCP package.
4) data packet end of transmission, closure connection.
If the above process uses traditional the server design method to realize, the means generally are requested with a thread unceasing read-in user's connection, then these request distribution for other work thread, these work thread distinguishes the repeat in cycles to complete the following work:
1) analyzes the request content.
2) transmits the RTP package, the transmission receives the RTCP package
3) judged data end of transmission, the closure connection. Server's structure as shown in Figure 3.
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