串流伺服器特性剖析

Abstract

一個串流伺服器主要由三個重要的模組所組成，這三個模組分別是『標準連線程序建立』、『RTSP信令溝通協調』以及『封包包裝和傳送』。

『連線建立標準程序』模組主要使用BSD Socket API來完成一個伺服器的初始化設置，也就是依串流程式的需求來建立TCP/UDP模式的socket。『RTSP信令溝通協調』模組主要允許串流伺服器經由RTSP信令來完成與用戶端的連線溝通，此部分的重點在於設定一個狀態機的機制來進行RTSP的信令。在『封包包裝和傳送』模組中，多媒體來源檔案的取得以及切割是經由封裝演算法來執行之，而一個結構化封包的產生即是經由某一種特定的封裝演算法而得到的，舉例來說， Live555串流伺服器所使用的M4V封裝演算法即是採用RFC 3016標準所建議的方式F。

在多工方面，Live555基於單一行程以及事件觸發的機制來達到串流伺服器的多工，此種多工型態所衍生的程式執行流程以及效能問題也是我們在本論文中所必須論述到的重點。

A streaming server will consists of three important modules, they are " Set up a standard connection procedure "," RTSP Signaling Negotiation " and " packet Packetization and Transmission " respectively.

" Set up a standard connection procedure "module uses the BSD Socket API to establish socket for the server, it can set up a TCP or UDP socket in accordance with the demand for our streaming program. In " RTSP Signaling Negotiation " module , it allows the Streaming Server to negotiate with Client via RTSP Signaling, the key issue is to set up a state machine for RTSP Signaling. In " packet Packetization and Transmission " module, multimedia source is retrieved and packetized through Packetization Algorithm , and we can generate a standard structurization packet with a specific PA, for example, the PA of M4V used in Live555’s Streaming Server is based on the TYPE(F) of RFC 3016.

For multiple clients connection at the same time，Live555 is based on Single-Process and Event-Triggered mechanism to reach the Streaming Server’s I/O multiplexing，and the relevant issues caused by specific multiplexing classification such as program flow path and performance are also significantly that we have to expound in this thesis.