Modern information technologies are transforming the way people learn. E-learning provides new possibilities for personalized learning at home or in the workplace, reduces the need for costly classroom training, and enables an optimal balance between tradi

and the desktop stream. A student is easily able to recognize the actual discussed part of a slide by comparing the slide to the video.Figure 2: Lecture Playback in RealOne Player Video and audio are synchronized to each other and then treated as one stream. The synchronisation between audio, video and Desktop is thus guaranteed. A text stream can contain additional information in the form of e.g. links or tables of contents. The operator of tele-TASK can position and dimension the streams freely (see figure 3).Figure 3: Layouting the streams Usually the video stream is put in field 1, the desktop stream in field 2 and the text stream in field 3. The composition of the streams is done by SMIL (Synchronized Multimedia) [16]. By supporting multiple input devices (Video, Audio and Desktop) it is possible to change the layout dynamically. In case of presenting high quality video scenes during the presentation, the desktop can be hidden and the video can be set up to fullscreen mode. Such cases often appear in medical presentations.2.3.4 Output FormatsAfter assembling the input streams, tele-TASK encodes them into a standard format. Currently 3 different formats are supported: 1. 2. 3. Real output Special low bandwidth format MPeg4The Real output directly supports the Real streaming server. Real streams can be set freely to arbitrary bit rates. Praxis has shown that 250 kBit/s is enough for high quality online lectures including video, audio and desktop. The software computes the Real stream in real-time, saves it to hard disk and streams it live to a streaming server. Parallel to the real encoding, tele-TASK encodes a special version for very low bandwidth. With only 38Kbit/s it is possible to provide video, audio and a perfectly renderd desktop. The only cutback is that animations on the presenter' computer cannot be shown. During a normal slide presentation the desktop s doesn'change a lot. The idea is to scan the desktop for changes and only the changes are saved and sent to t the client in a compressed way. Figure 4 shows a slide in which two new lines have appeared.