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.
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
Figure 4: Slide with two new lines (marked) tele-TASK grabs out the changed area and computes the exact difference between the old and the new state. Figure 5 presents the exact difference between the two states.Figure 5: Changes between two slides Only the white areas are saved and sent in a compressed way. For 90 minute slide presentation including annotation we save and send about 200 to 300 desktop updates. In total we need about 1 Megabyte for the complete high quality (about 600*400 Pixel) desktop. [17] shows an example. The last output format of tele-TASK is MPEG4. The software computes MPEG4 streams in real-time. Like the Real output the MPeg4 stream can be saved to harddisk and sent to a streaming server. Apple provides the free and open-source MPeg4 streaming server Darwin, which can be used directly. For each output format the usually pre-installed standard players like Realplayer, MS Mediaplayer, Quicktime Player can be used. By supporting these standard players, we fulfill the most required feature: Make the access as easy as possible for end-user.2.4 T-Cube – Make the production as easy as possibleBesides of the easy call up of learning content for the student, another quite important feature for distance education is to break down barriers for the production of electronic content. With T-Cube, a high integrated easy to use device based on tele-TASK is given. The T-Cube is a small computer in the shape of a cube. The T-Cube has two network devices. One is for connecting to the local network and the second for the presenters computer. The interface for the local network has to be configured once by a system administrator. The second one provides a direct connection to the local intranet, not depending on the network settings on the connected laptop. This feature is also done by tele-TASK. It masquarades the range of all IP-adresses including the faking of all possible gateway IPs. The big advantage is that every lecturer can use his own laptop without configuration. The laptop can be connected directly to the T-Cube and has access to the local intra-/internet without having to be adjusted. This is very important for conferences where presenter want to use their own laptop. Once connected to the T-Cube, a small software is started on the laptop via a web-interface. This software allows to export the desktop and to control the T-Cube. By the use of hotkeys the lecturer can start/stop/pause the lecture. By using the integrated solution the lecturer doesn' need much knowledge about the system in t use. He can easily start and stop the session by himself. Cameras and microphones can be connected directly to the T-Cube. The streams can be sent to the streaming server and saved on a local harddisk parallel. After a presentation a CD/DVD with the recorded content is burned automatically. The configuration of the tele-TASK sofware can be done by a webinterface or by an external program. The T-Cube does not need a monitor, keyboard or mouse. It is just a black box which can be switched on and off.