多使用者互動式隨選視訊有線電視網路系統之研製

Abstract

由於網際網路的流行，加上多媒體研究的日益成熟，結合此兩種技術可產 生各種應用服務，將對人類未來的生活型態造成深遠的影響。其中隨選即 播視訊服務系統(VOD)是將影片儲存在影片伺服器中，用戶端經過網路與 影片伺服器連接，影片伺服器便能提供類似錄放影機快、回轉，暫停，播 放的功能 ; 而且用戶也能根據自己的時間安排收看影片節目。 因為 VOD 系統具有處理資料量龐大、具互動性與連續性播放之特性，因此我們 設計了一個較低成本的VOD系統架構----CVOD系統架構,在此系統架構中以 生產線式檔案系統架構 ( Pipelining File System;PFS ) 來作為 CVOD 之檔案系統。PFS是具有集中管理,分散控制的檔案系統,適合處理多媒體 資料;而在網路傳輸系統方面,用有線電視網路做為本系統的主幹網路,我 們將數據網路與影片傳輸網路分開,以單一頻道建立成為數據網路頻道,作 為供命令資料傳輸之用,而其他頻道則做為下傳影片視訊之用,每個客戶以 專屬的頻道為其傳送影片,所以本系統能提供高品質的播放畫面。 利 用這樣的架構，我們實際製作了一個 CVOD 的系統,以自行設計之CNC- RS115控制器將數據網路建立於13頻道上,本系統提供影片.、客戶管理系 統,影片的VCR功能,在多使用者環境下的允許控制,影片存取機制與頭端和 客戶端資料傳輸的安全檢查及系統擴充性,且進一步的驗證本系統來自網 路上的系統命令之能力，足以承受系統實際運作時的忙碌工作分派。 Because the researches on both Internet and multimedia are popular,the integration of these two technologies will produce some important application services that have great influence on our futher life.A VOD system stores video data in the video server and clients connect to the video server by using network. By communication over network,the server can provide clients VCR-like functions such as fastforward,fastbackward,pause and play,etc.Thus users can choose their desired time to watch programs. VOD system has the properties of a mass data, interactive and continuous playback.So we design a low cost VOD system architecture(CVOD system) to satisfy above issues.CVOD system architecure uses "Pipelining File System"(PFS) as its file system. Because PFS is a central control, distributed processing file system, it is suitable for processing multimedia data;CVOD system makes use of CATV network as backbone network. Data network is separate from video transmission network, a specific channel is established as a data network for transmitting data command. All other channels can be chosen to transmit video data on demand. Every on-line user has his own channel to receive video data from the cable network. This mechanism can reach high qualityof program playback. By making use of above architecture, we implement a CVOD system. The data network of this system is established on the channel 13 by a specific designed cable network controller - CNC-RS115. CVOD systemhas video and user account management systems and also composes the properties of VCR-like functions,admission control in multi-user environment, security monitoring and scalibilty.We also verify the system ability for handling commands from clients and analysis the result to prove this system architecuture has capabilty to handle all commands that clients send.