行動式多媒體推播與跨終端機換手系統設計實做

Abstract

在過去的幾年裡，遠端學習越來越具有吸引力。然而以往遠端學習多半著重在於觀看者可以從遠端參與教學活動，對於演講者的遠端教學機制著墨較少。再者，隨著網路頻寬的提升與串流技術的進步，使得多媒體串流服務變得可行。因此在這一篇論文裡我們設計並實做一個多媒體遠端學習系統讓觀看者和演講者都可以在遠端參與教學活動。觀看者在這個系統架構之下除了可以看到目前正在進行的演講、教學之外，也可以看一些預先錄製好的教學節目。 此外，終端設備技術的進步也使得終端設備更多樣化。使用者可能會在不同的場合使用不同的終端設備，或甚至同時使用多個終端設備。然而當使用者在觀看多媒體串流的時候如果想要變更終端設備，就必須到另一台終端設備重新手動操作取得串流的過程，無法把原本正在觀看的串流轉換到另外一台終端設備。因此我們的系統也提供跨終端機換手的功能。而且在進行跨終端機換手的時候，我們可以根據使用者的設備特性來調整多媒體串流的bitrate。 最後，我們也提出不同的方法來傳送教學投影片的影像。在這篇論文裡，我們描述三個不同的方法並且實做其中的一種。使用這些經過設計的方法來傳送投影片影像時，不用消耗太多頻寬就可以讓觀看者看到清晰的投影片影像。

During the past few years, distance learning has gradually become more and more attracting. However, most of the previous research focuses on making the audience able to learn remotely through internetworking. Little research has been done to increase the flexibilities of teaching at a distance. Moreover, with the increase of network bandwidth and the advance of streaming technologies have made multimedia-streaming services feasible. Therefore, in this thesis, we design and implement a multimedia distance learning system that could make the audience and speakers take part in teaching activities from the distance. In this system, the audience could watch not only the on-going speeches or teaching programs but also some teaching programs, which have previously been recorded. Furthermore, the advance in terminal technologies also makes terminal devices versatile. It is now possible that a person may use different devices in different occasion or even use multiple devices simultaneously. However, if a person wants to change device in the middle of a multimedia service he needs to re-instantiate the multimedia service, instead of transferring he multimedia-streaming that they were using on one of his device to the other one. Therefore, we also provide inter-device handoff functionality in our system. Besides, we could also adjust the bit-rates of the multimedia streaming according to the characteristics of the devices in use while performing an inter-device handoff. Finally, we also present different methods to deliver the images of teaching slides. In this thesis, we describe three different approaches to delivering the slides images, and have implemented one of these three different approaches. The approach has been carefully designed to transfer slide images that is clear to audience without consuming much bandwidth.