本論文是參與工研院及威達雲端的高鐵上網計畫中的高鐵即時影音平台開發
的成果，該平台主要是利用專屬於高鐵上網的WiMAX 網路，將即時影音資料傳
送到高鐵列車上，再透過Wi-Fi Access Point (AP) 將影音資料以multicast 方式傳送給高鐵列車中的使用者。而當中Wi-Fi IP multicast 所造成的封包遺失，則是使用Application Layer - Forward Error Correction (AL-FEC) 技術去修補。先前該平台只完成了頭端系統軟體及Windows 版。
　　本論文所提出的Android client 端程式，是搭配高鐵即時影音平台頭端
系統軟體中的WiFi multicast 串流伺服器所開發的。爲了提升使用者介面的操
作流暢度及降低使用者介面的操作複雜度，我們提供了以下的功能: 快速的頻道
切換(fast channel switch)、使用WinRT 平台內建的media player 作為播放器、透過pre-cache 技術來降低channel switch 時所耗費的時間…等功能。此外，為了搭配Android 平台內建的media player，我們在Android 版的client 端中內建了RTSP Relay Server，除了支援RTSP (Real Time Streaming Protocol) 協定外，還處理了multicast RTP 串流服務在AL-FEC 解碼後轉換為unicast 傳送時的相關問題，例如: 影音傳送速度控制(flow control) 及影音同步(audio and video synchronization)…等功能。

This paper is the achievement of participation of the mobile TV streaming service project provide by ITRI (Industrial Technology Research Institute) and VeeTIME Corporation. This mobile TV streaming service is operating base on the WiMax
internet service for THSR (Taiwan High Speed Rail). This system using the WiMax internet service to deliver media data to the WiMax MS (Mobile Station) on the high speed cars. The WiMax MS will deliver the media data by many Wi-Fi AP (Access Point) in the cars to client in IP multicast and UDP (User Datagram Protocol) which is unreliable. The system use Application Layer - Forward Error Correction (AL-FEC) to fix the problem of packets loss. The client of this system haven’t implement on Android before.
This paper propose a Android client to receive the media data delivered by the mobile TV streaming service’s media streaming server which send packet by Wi-Fi IP multicast. The goal of this paper is provide a good user experiment. For this purpose, we propose these functions - Fast Channel Switch, using an embedded player which can be embed in UI, design Pre-Cache module to reduce the period of buffering, etc. Moreover, we also design a RTSP (Real Time Streaming Protocol) Relay Server for embedded player on Android. RTSP Relay Server not only support RTSP, but also handle the issues about the data decoded by AL-FEC. For instance, The Flow control issue and the audio and video synchronization issue.

Table of Contents i
List of Figures iii
List of Tables iv
List of Formula v
1 Introduction 1
2 Background 4
2.1 Application Layer – Forward Error Correction (AL-FEC) . . . . . . . 4
2.2 Real-time Transport Protocol (RTP) and RTP Control Protocol (RTCP) 5
2.3 Session Description Protocol (SDP) . . . . . . . . . . . . . . . . . . . 6
2.4 Real Time Streaming Protocol (RTSP) . . . . . . . . . . . . . . . . . 8
2.4.1 OPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4.2 DESCRIBE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4.3 SETUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4.4 PLAY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4.5 TEARDOWN . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4.6 RTSP Server State Machine . . . . . . . . . . . . . . . . . . . 11
2.5 Android . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 Related work 14
3.1 AL-FEC over THSR . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 Other AL-FEC related works . . . . . . . . . . . . . . . . . . . . . . 16
4 System Requirement 17
5 System Architecture and Flow Chart 19
5.1 System Architecture Overview . . . . . . . . . . . . . . . . . . . . . . 19
5.2 UI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.3 RTSP Relay Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.3.1 RTSP Relay Server Overview . . . . . . . . . . . . . . . . . . 22
5.3.2 RtspComm and RtpComm . . . . . . . . . . . . . . . . . . . . 23
5.4 Pre-Cache . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.5 System Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.5.1 Flow Chart of Interaction Between Activity and RTSP Relay
Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.5.2 RtspComm Flow Chart . . . . . . . . . . . . . . . . . . . . . . 27
6 Implementation Issues 31
6.1 Fast Channel Switch Based on Pre-Cache Model . . . . . . . . . . . . 31
6.2 RTCP Delivery in RtpComm . . . . . . . . . . . . . . . . . . . . . . 32
6.3 Stream Flow Control Issues . . . . . . . . . . . . . . . . . . . . . . . 32
6.4 Audio and Video Synchronization Issue in RtpComm . . . . . . . . . 34
6.5 Buffer Control Issue . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7 Performance Evaluation 36
7.1 AL-FEC Decoding Time v.s. AL-FEC Protection Period for Wi-Fi
IP Multicast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
7.2 Buffering Time with Pre-Cache v.s. Buffering Time without Pre-Cache 38
7.3 RTP Packet Loss Rate for Wi-Fi IP Multicast . . . . . . . . . . . . . 39
7.4 Power Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
8 Conclusion and Future Work 42

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