串流伺服器資料解析及封包包裝

Abstract

現今在即時多媒體應用上的主要課題在於即時(Real-time)的傳輸實況影音與已儲存的多媒體檔案，而多媒體串流技術可以讓使用者在下載多媒體檔案的同時可以先觀賞到已下載的部份，此項技術使得使用者不需要花費下載時間與硬體空間來儲存多媒體檔案。 而一個多媒體串流伺服器包含了三個主要的模組，這三個模組各別為: 「標準連線程序建立」、「RTSP信息溝通協調」與「封包包裝和傳送」。而在本論文中主要討論是「封包包裝和傳送」模組，此一模組是整個伺服器運作的重心所在，最主要在於實現檔案資料的解析與特定的封裝演算法，產生適合網路環境的封包並且傳輸。 從IETF所制定的標準中可以知道RTP對不同影音檔案皆有其建議的封裝方式，本篇論文主要是針對這些封裝方式做探討，著重於影音檔案資料parser的運作機制，且提出一個架構在「封包包裝和傳送」模組內的RTP封包演算法，並藉由分析Live555此套open source的架構做為輔助及驗證RTP封包演算法是如何被實現的，在本論文中，所要探討的主要在於已儲存的多媒體影音檔案的部份，並以MPEG家族的影片格式做為實驗對象。

Today, the main points of real-time multimedia applications are the transmission and the play of live video or stored files. Streaming technology allows people to enjoy the multimedia contents while downloading them. With the advantages of this technology, users don’t need to spend extra time when downloading multimedia contents or spare extra memory space to save them. 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. This discourse focuses on the module of "packet Packetization and Transmission " which is the key point to operate well in server, and to realize the analysis of file information and specific packetization algorithm which produces the packet adapting the internet environment. Because of standard define by IETF, we can know that different multimedia files have different RTP payload formats. The topics of this thesis mainly discuss the multimedia files’ parsing, Packetization, and transmission modules. Finally, we analysize the open source “Live555” to verify how the above three modules are implemented.