近年內，網際網路已經十分普及，由學校拓展到整個社會。它已經完全改變現代人擷取資訊的方式，以往我們會看報紙查詢電影場次與時間、排隊買火車預售票、看氣象報導了解天氣，時至今日，大部分的人都會將這些工作透過網路完成。隨著無線區域網路與第三代行動電話技術的成熟，全方面上網的時代必將達成，透過手機或是手持型電腦(PDA)，使用者不需透過桌上型電腦便可以與網際網路資訊交流。

在無線區域網路中，使用者可以透過PDA與無線網路卡和網路聯繫。PDA具有輕便與行動化的特性，使用者可透過輕巧的PDA與適當的瀏覽器瀏覽網頁。相對地，為了增加行動性所減少的體積與重量，同時也減低了PDA的功能，PDA的中央處理器與記憶體大小相較於桌上型電腦大幅下降，這種情況再瀏覽一般HTML網頁時尚不明顯，但如果使用者要在PDA端瀏覽含括影片(video)物件的SMIL網頁便會產生許多問題。讀取XHTML網頁時，PDA可將整個網頁中相關的圖片、文字、動畫下載至記憶體之後播放，但在SMIL中，影片物件的容量並不允許PDA如此。此時便必須使用串流(streaming)技術。

使用串流的方式，瀏覽端可在下載多媒體檔案的同時播放此多媒體檔案。串流技術可分為兩種，一為HTTP串流，一為RTP串流。HTTP串流是目前最廣為接受的串流技術，但是它的設計是以一般電腦特性制定，並未考慮到如PDA之類資源受限的裝置。

本論文針對串流技術做詳盡的介紹，說明HTTP串流的限制為何？與RTP串流相比優劣處為何？如何修改HTTP串流技術，使得PDA等資源受限的裝置上可以瀏覽多媒體？此外，根據所提出的串流技術，我們更實做出了一個跨平台的WSMIL瀏覽器，論文中將針對此瀏覽器的發展環境、專案架構、各多媒體類別與核心類別的功能用法與相互間的關係做詳盡的介紹。透過此WSMIL瀏覽器與WSMIL proxy，使用者便可在PDA端透過無線網路瀏覽多媒體。

In resent years, Internet is quite popular in schools or even the whole society. It changed the way people collect the information now. In the past, we check the timetable for the movies、wait in a line to buy the advance booking train tickets、get the information about weather from the weather reports on TV, however, now these jobs could be done on the Internet. Since the technique of wireless LAN and 3G is getting more complete, the era of omnifarious application of Internet is coming. Users can exchange information on the Internet through cellular phones or PDA without using desktops.

In wireless LAN, users get on the Internet through PDA and wireless network card. PDA has the feature of lightness and mobility; by using it and an appropriate browser, users can browse websites on the net. However, in order to increase the mobility of PDA, it’s necessary to eliminate the size and the weight of it. Under this condition, the function of PDA is decreased. Compared to those of desktops, the CPU speed and RAM size of PDA are deducted. Though it would not be noticed while users are browsing general HTML websites, problems occur while users use PDA to browse SMIL website which contain video objects. While browsing XHTML websites, PDA downloads the photos, words, flashes on the website to RAM and then display them. However, because of the size of the video objects on the SMIL websites, PDA is not allowed to do so while users are browsing SMIL websites. Under this circumstance, the streaming technique is what we need.

By using the tech of streaming, the browser side downloads the multimedia file and displays it at the same time. The tech of streaming can be divided into two types. One is HTTP streaming; another is RTP streaming. HTTP streaming is the most widespread one but it is designed to fit the general PCs. It is not under consideration to use HTTP streaming on resource-constrained devices, such as PDA.

This thesis will focus on the tech of streaming and provide an explicit description of the streaming tech. We will also discuss the restriction on HTTP streaming; the comparison between RTP streaming; how to modify the tech of HTTP streaming to be used on PDA or other resource-constrained devices? In addition, by applying the streaming tech we propose here, we implement WSMIL browser which can cross platform. In this thesis, we illustrated the developing environment for this browser, architecture of project, an explicit introduction of multimedia classes and kernel classes, the function and usage of them and the relation between each other. By applying WSMIL browser and WSMIL proxy, users are enable to browse multimedia through wireless LAN on PDA.

Chapter 1 Introduction 01

Chapter 2 Background and related work 03
2.1 SMIL and WSMIL 03
2.1.1 SMIL 03
2.1.2 WSMIL 03
2.2 Embedded System 04
2.3 Transport layer protocol 05
2.3.1 TCP 05
2.3.2 UDP 06
2.4 802.11 06
2.4.1 MAC Layer 06
2.4.2 Physical Layer 07
2.5 Qt 08
2.5.1 Introduction 08
2.5.2 Widget 08
2.5.3 Qt ‘s architecture 09
2.5.4 Qt/E 10
2.6 UML 11
2.7 MPEG 12

Chapter 3 Multimedia Streaming Technology 15
3.1 Introduction of Multimedia Streaming 15
3.2 HTTP Streaming 15
3.2.1 What is HTTP? 16
3.2.2 What is HTTP Streaming? 16
3.2.3 Disadvantage of HTTP Streaming 17
3.3 RTP Streaming 17
3.3.1 What is RTP? 18
3.3.2 What is RTP Streaming? 18
3.3.3 Disadvantage of RTP Streaming 20
3.4 The Comparison between HTTP and RTP Streaming 19
3.5 WSMIL Streaming 21
3.5.1 What is WSMIL Streaming? 21
3.5.2 Messages in WSMIL Streaming 22

Chapter 4 Multimedia Streaming on WSMIL browsing system 25
4.1 Environment of WSMIL browsing system 25
4.1.1 Network topology 25
4.1.2 Characteristics of target devices of WSMIL browser 25
4.2 WSMIL-based Streaming Mechanism 26
4.2.1 Client-Initiated and Server-Initiated Streams 26
4.2.2 WSMIL-based Streaming Mechanism on resource-constrained device 26

Chapter 5 WSMIL Browser Architecture 33
5.1 Browser backbone 33
5.2 The Display Packet 36
5.2.1 Text Objects 37
5.2.2 Image Objects 38
5.2.3 Animation Objects 39
5.2.4 Video/Audio Objects 40
5.3 The Kernel Packet 44
5.3.1 WSMIL Parser 44
5.3.2 Interface Class 46
5.3.3 Synchronization Unit 48
5.4 WSMIL browser snapshot 48

Chapter 6 Conclusions 51

Reference 53

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