The Design and Analysis of a Broadcasting Scheme with Supporting VCR Functions for Near Video-on-Demand Systems

碩士論文[[abstract]]本論文中提出了一個架構在類隨選視訊系統環境下可提供VCR功能的廣播策略。在先前許多研究者所提出的廣播策略中，只要STB (Set-Top-Box)能提供足夠的buffer來存放影片片段資料，則用戶端可執行暫停 (pause)、倒轉 (rewind)等特定的VCR功能。但是在快轉 (fast forward)方面，除非事先已將所需影片片段從伺服器下載至用戶端的STB方能使用戶端執行快轉播放。此一現象引發我們提出一個新的VCR廣播策略。根據預先儲存的觀念，我們所提的方法除了可支援暫停、倒帶等VCR功能外，更可在特定條件下支援快轉的服務。在我們的廣播策略中，會預設影片的前面p個片段是不提供快轉的功能。因為就一般市面上的影片而言，在影片的最前面總會有一些廣告或是版權聲明，當然在業者的商業考量上，會希望用戶觀賞到廣告或是版權聲明，所以前面部份片段不希望用戶忽略跳過是一個合理的假設。我們先將影片片段S切割成n個等長片段且經由k個頻道來播放。用戶端同時下載k頻道的影片片段至STB內並選擇適當的影片播放。每當用戶端想要執行d倍速快轉時，根據我們的廣播策略，存於用戶端的STB中的影片片段及持續下載自k個頻道的影片片段必能趕得及用戶端所需的快轉播放影片片段。也因此我們所提出的廣播策略不僅能提供用戶端暫停、倒轉等服務，也能提供用戶端快轉的服務。[[abstract]]This thesis presents a broadcasting scheme with supporting VCR functions for Near VOD systems. The previous broadcasting schemes could support specific VCR functions, e.g. pause, rewind, etc., without fast forward when the client’s buffer is sufficiently large. Therefore, it motives us to propose a novel scheme with supporting VCR functions. Based on the pre-saving concept, our method can support more complete VCR functions. We first consider a movie S divided to n equal-length segments and k channels available. Each client downloads the movie segments from k channels simultaneously to client’s STB. Meanwhile, each client views the movie segments in order. When a client plays d-speed fast-forward, the needed segments has been stored in client’s buffer or will be downloaded in time. Consequently, our broadcasting scheme can provide more VCR functions than the previous methods