臺灣博碩士論文加值系統

隨著數位視訊技術的進步以及網際網路、無線網路的快速發展，利用網路傳輸影像資訊的需求持續地在增加，影像傳輸技術也越來越受到重視；相關的應用包括：視訊會議、影像串流、數位視訊廣播等，而近年來非常熱門的P2P (peer-to-peer)網路亦整合了影像傳輸技術提供網路電視服務和大量的影音資訊分享。然而，由於網路傳輸環境的不穩定，將有封包遺失和位元錯誤之不可避免的情況產生，因此，如何提供可信賴、穩定的影像傳輸成為一個極需解決的問題。
多重描述編碼(Multiple Description Coding, MDC)技術能夠有效抵抗資料經由網路傳輸過程中產生的封包遺失，並具有優秀的錯誤更正能力。利用多重描述編碼技術，可在易發生錯誤的封包網路上提供穩定的影像傳輸。首先，來源影像在發送端會被壓縮編碼成為兩組或多組彼此相關但可獨立解碼之位元流，每組位元流就是對於來源影像的一種描述。接著利用網路上不同路徑傳送至接收端，而根據網路錯誤情形，接收端將可重建出不同品質的影像。由於可獨立解碼的特性，只要收到一組位元流，即能重建出可接受的影像品質，隨著接收到越多組位元流，重建出來的影像品質也越高；當位元流流失時，亦可利用其他完整收到之位元流資訊以重建影像。
在本論文中，我們提出一個以多重描述編碼技術為基礎且每一個描述(Description)皆獨立使用SPIHT (Set Partitioning In Hierarchical Trees)壓縮演算法的強健影像傳輸系統，利用SPIHT擁有漸近性的編碼特點，編碼時其位元率能被精準的控制進而達到高效率的編碼，而本架構也加入了額外之嵌入資訊(Embedded Information)支援完整的錯誤更正機制；根據實驗的結果顯示，我們所提出之強健影像傳輸系統擁有較佳的錯誤更正能力，對於抵抗易發生錯誤之封包網路的表現超越了傳統上以錯誤隱藏方式之多重描述影像傳輸系統。最後此系統將應用在視訊編碼系統上，結合適當的網路傳輸技術，將能提供更多可信賴、穩定的影像傳輸服務。
關鍵字：多重描述編碼、影像壓縮、封包交換網路、SPIHT、視訊編碼

With the advanced progress of video coding and the highly progressive development of wired/wireless network, the need to transmit image information over wired/wireless network is increasing dramatically and the technology of image transmission attracts lots of attention. The associated application includes: video conferencing, video streaming and digital video broadcast etc. The P2P (peer-to-peer) network, which is extremely popular in the recent has also integrated the image transmission technologies to provide the network television service and the share of massive video and music information. Because the network transmission environment is unstable, the packet loss and the bit error are inevitable. Hence, how to provide reliable and stable image transmission is an important issue.
The multiple description coding (MDC) can make the information resistant against to the packet loss over noisy network and provide outstanding error resilience ability. First, one origin image is spilt into to two or more bit streams by encoder and each of the bit streams has correlation between each other, but it can be decoded independently. Each of the bit streams is one of the descriptions of the origin image. Second, these bit streams are transmitted to the decoder over different noisy channel. According to the different network environment, the decoder can reconstruct the various qualities of images. Because decoding is independent, when the decoder receives only one bit stream, an acceptable image can be achieved. When more and more bit streams are received by the decoder, the quality of the reconstructed images becomes better. When the bit streams are lost, the decoder can use the information of other bit streams to accomplish error concealment.
In this thesis, we proposed a robust transmission technique of image based on MDC and each of the descriptions is encoded by Set Partitioning In Hierarchical Trees (SPIHT). Using the characteristic of gradation encoding in SPIHT, the bit rate can be controlled accurately and result in an efficient coding. The robust transmission technique also embeds some supplementary information to deal with the packet loss. According to the simulation results, the proposed technique has better error resilience ability and outperforms other image transmission technique based on MDC over noisy channel. Finally, the proposed technique has been applied to distributed video coding system and the simulation results indicate it did provide a more reliable and more stable video transmission service under variable network channel.

Keywords: Multiple Description Coding, Image Compression, Packet-Switch Network, Set Partitioning In Hierarchical Trees, Video Coding.

中文摘要 I
Abstract III
誌謝 V
第一章 緒論 1
1.1 研究背景及動機 1
1.2 概述各章節內容 2
第二章 基本理論介紹 3
2.1 離散小波轉換 3
2.2 SPIHT原理介紹 6
2.3階層式影像傳輸系統原理介紹 9
2.4多重描述傳輸系統原理介紹 10
第三章 使用多重描述編碼及嵌入性資訊之強健影像傳輸系統設計方式 12
3.1 分散性多重描述法則 12
3.2 頻率域上之嵌入性資訊取得與利用 15
3.3 應用於封包交換網路中之模擬結果 22
第四章 結合低密度同位檢查碼應用於分散式視訊編碼系統設計方式 39
4.1 分散式視訊編碼架構 39
4.2 低密度同位檢查碼(LDPC Codes) 42
4.3 結合強健影像傳輸之分散式視訊編碼系統模擬結果 51
第五章 結論與未來展望 84
參考文獻 85

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