中文摘要

本論文提出了一個階層式多重描述編碼（Layered Multiple Description Coding ; LMDC）的架構，適用於可調式的視訊傳輸系統，當面臨到異種的網路結構（Heterogeneous networks）時，如何提供串流視訊服務到不同能力的客戶端，提供了好的解決方法。

本論文的LMDC系統是一個混合了離散小波轉換（Discrete Wavelet Transform ; DWT）和H.264的組合，在此演算法中，一個輸入的視訊序列會先經由DWT分解成一個基本序列和數個具正交性質的補充序列，每一個序列再經由H.264來有效利用空間與時間上的相關性進行編碼。使用本論文的LMDC系統，當在網路具有傳送優先順序的條件下提供串流服務時，相較於只使用H.264完成的階層式編碼系統，LMDC系統除了能提供更廣泛的碼率選擇，還能在網路頻寬發生變化時，使視訊品質能平滑的進行變化。且當網路不提供優先順序時，相同於在LMDC系統中使用的位元流，仍然可以被靈活編排成單純的多重描述位元流，來增強可調性與強健性傳輸。

本論文所提出之LMDC等方法也可以很容易與其他可調式編碼技術如MCTF等整合，而進一步擴展系統之可調性。不僅如此，現有的H.264軟體與硬體可以直接使用於實現本論文提出的演算法，因此LMDC系統在提供可調式視訊串流的實現上，是一個低成本解決方案。且LMDC系統比起motion JPEG2000和MPEG4具有更好的效能；另外在相同的碼率條件下進行資訊傳輸，LMDC系統的效能也勝過H.264-based simulcast的系統。

關鍵詞：可調式編碼，階層式編碼，多重描述式編碼，階層式多重描述式編碼

ABSTRACT

This paper presents a layered multiple description coding (LMDC) scheme for a scalable video delivery system which operates over heterogeneous networks and distributes real-time streaming video to diverse types of clients. The LMDC is a hybrid combination of discrete wavelet transform (DWT) and H.264. In the algorithm, an input video sequence is first decomposed into a fundamental sequence and a number of orthogonal supplemental sequences using DWT. Each sequence is encoded by H.264 for effective exploitation of spatial and temporal correlations. As compared with its layered coding counterparts for streaming over networks providing transportation priotization, the LMDC offers a wider range of bit rates and a smoother transition in video quality for variations on the network capacity. When the transportation priotization is not available, the same LMDC-encoded bitstreams can still be reused to form a pure multiple description bitstream for scalable and robust transmission. The existing H.264 codec software and hardware can be reused for the implementation of the proposed algorithm. The LMDC therefore is a low cost solution to the realization of the scalable video streaming. The LMDC has superior performance over motion JPEG2000 and MPEG4. It also outperforms the H.264-based simulcast systems subject to the same rate for information delivery.

Keywords：Scalable Coding, Layered Coding, Multiple Description Coding, Layered Multiple Description Coding

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