A study of developing a video conference system for network multimedia application

本篇論文主要論述有關在個人電腦上發展一套視訊會議系統所使用的方法 和其相關技術。視訊會議系統所強調的是即時性的大量資料傳輸。對於這 麼龐大的資料傳輸其解決之道可以從兩方面著手：一為擴大網路的頻寬， 另一為使用壓縮技術減少資料傳輸量。本篇論文乃利用DVI (Digital Video Interactive)壓縮技術針對光纖網路(FDDI) 和乙太網路( Ethernet)提出不同的策略，以傳送視訊會議其所需的大量視訊畫面和音 訊資料。並採用WINSOCK的網路應用程式介面來開發系統，使得系統具有 高度的可攜性。本篇論文所發展的視訊會議系統簡稱VICO (VIdeo COnference)。VICO系統採用功能模組化的方式來設計，主要是由一個系 統核心單元和視訊音訊子系統、網路子系統、檔案傳送子系統、電子白板 子系統、人機介面子系統五個子系統所組成的。VICO系統除了傳送視訊音 訊資料外，也提供電子白板功能，以便讓雙方使用者能在線上同時討論問 題，而透過所設計的剪貼功能，電子白板子系統更可和別的應用軟體交換 圖形、文字資料，以輔助整個視訊會議能更有效率的進行。另外系統也提 供了列印資料、網路遊戲、檔案傳送等功能。整個VICO系統經測試結果顯 示，VICO系統在FDDI網路和ETHERNET網路上，以每秒25張FRAME，解析度 為256x240大小之視窗來播放時，其延遲的時間大約在0.1-0.5秒之間，不 過由於VICO系統採用捨棄太小的視訊FRAME之方法，為了顧慮同步問題所 以有些音訊資料也被捨棄，故在聲音方面有些微的抖音和不連續的現象。 而在電子白板的資料，其也可以同步更新雙方資料，並可直接從印表機輸 出。在操作介面上，系統所提供選單、立體式按鈕、浮動式選單均可以很 靈敏的操作，整個系統的操作不會有反應遲鈍的現象。本文結論為利用壓 縮技術和適切的運用網路傳輸、程式設計技巧，我們將可以在PC之區域網 路上發展一套視訊會議系統。而採用模組設計方法和利用WINSOCK的網路 程式設計介面，將使得整個系統具有高度的擴充性和可攜性。近年來電腦 各方面進步的速度非常的快，如發展高頻寬的網路ATM、製造更快的個人 電腦pentium和更多的壓縮技術MPEG等被公佈，這些技術將使得發展多人 視訊會議系統或在廣域的網路(WAN)上發展跨區域的視訊會議系統的環境 更加的成熟。This paper presents an application of such a combination which results in the development of a video conference system based on personal computer environment referred to as the "VICO" system. Video conference emphasizes the requirement of the real- time medium delivery for a large mount of data such as video and audio data. This can be achieved by increasing the network bandwidth and by adopting compression techniques to decrease the amount of data needed to be transferred in the network. The compression techniques we adopted in the VICO system is based on the Intel's DVI technology (Digital Video Interactive). The platform used for the VICO system is based on FDDI and Ethernet where various Windows programming techniques are adopted. In particular, WINSOCK API network programming techniques are utilized for the system development. VICO system is designed to be composed by several modules each of which is developed to deal with the corresponding medium. The modules include a system kernel system, video and audio modules, file-transfer module, network module, whiteboard modules and finally the user interface module. Experimental results collected for the VICO system show that a delay time in between 0.1 and 0.5 seconds will be detected for a frame of 256x240 resolution when using a FDDI network with transmission rates of 25 frames per second. The audio signals can be detected to be a bit of discontinuity due to the abortion of part of the video and audio data. We conclude in this thesis that the approach used in the VICO system by creating several modules for the corresponding medium is of use for the system development allowing easy portability and expansibility. The development of the VICO system has demonstrated that by taking the advantage of the compression techniques and skills of the network programming we can construct a video conference system based on personal computer network