Distance Education Using Linux and the MBone
The primary components of the distance education software used at NC State are the MBone tools. These are vic, rat, wbd, and sdr are available for download in binary and source form at University College London's (UCL) web site at http://www-mice.cs.ucl.ac.uk/multimedia/software/. vic is an MBone video-conferencing tool. It was originally developed by Steve McCanne and Van Jacobson at the Lawrence Berkeley National Laboratory (LBNL) Network Research Group. The version being used at NC State is currently under development at UCL. This version provides video-capture support using Video4Linux, so many existing video-capture cards are compatible with it. It incorporates a number of codecs including H.261 and H.263. It provides controls to adjust frame rate, bandwidth, and video quality, as well as many other options. Users can switch between thumbnail and full-screen video windows, and switch between a number of video formats. vic runs in multicast- conference mode or point-to-point-unicast mode.
The Robust Audio Tool (rat) is an MBone audio-conferencing tool. rat was developed by UCL's Networked Multimedia Research Group. There are two versions of RAT: a stable, toll-quality (i.e., telephone-quality) version 3, and an improved, though experimental, high-quality version 4. rat supports both ALSA (Advanced Linux Sound Architecture) and OSS (Open Sound System), so it is compatible with a large number of sound cards. rat provides a number of audio codecs, as well as packet-loss concealment schemes. Other features include automatic gain control, silence suppression and encryption. rat also provides a graphical interface showing conference participants and audio levels. Like vic, rat can operate in point-to-point-unicast mode or in multicast-conference mode.
wbd is an MBone shared whiteboard. It allows a number of participants in a conference to share a single whiteboard workspace. It was originally written by Julian Highfield at Loughborough University. The most recent development work on it has been done by Kristian Hasler at UCL. wbd is compatible with the original LBNL whiteboard, wb, developed by Steve McCanne. Because wb is available only in binary form for UNIX platforms, Julian Highfield wrote wbd primarily to fill the need for a Windows version of wb. Since the source is freely available, we have chosen to use wbd over the binary-only wb on Linux. wbd has a standard set of whiteboard features, such as font, color and line-width options, text input capability, drawing tools and various page orientations. wbd can import both PostScript and text files. wbd was designed to work in both point-to-point and shared multicast modes, though currently only the multicast mode functions properly in Linux.
Instead of each user in a conference connecting to every other user, MBone users join a multicast group. Anything sent to the group is received by all current members of the group. None of the MBone tools discussed so far provide any means of locating or advertising these groups. This is accomplished through the session directory tool, sdr. In a sense, the session directory is like a television guide which shows all the currently available “shows” on the MBone. sdr was originally written at UCL and was modeled after another LBNL tool called sd. When the user loads up sdr, a listing of all public and private MBone sessions appears. To get more information about a specific session, the user clicks the session name. To join a session the user clicks the join button for that session and sdr then loads up the various tools needed to participate in the session. To create a new session, the user clicks the New button and enters various information about the session. sdr then generates the multicast addresses and advertises the session for other users to see.
The bandwidth requirements for the MBone tools are relatively low by current standards. Each video source requires only about 128KBps at a rate of ten frames per second. The audio requires about 64KBps at telephone quality. Higher frame-rate video is possible, but we've found that high-quality whiteboard data in combination with good-quality audio more than compensate for the slow video. The video mainly orients the participant and provides visual cues, while the actual content is provided via the audio and whiteboard data. For some classes, it is more important to provide full-motion video, and when adjusted appropriately, vic can provide this.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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- Stunnel Security for Oracle
- The Firebird Project's Firebird Relational Database
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- SUSE LLC's SUSE Manager
- Managing Linux Using Puppet
- My +1 Sword of Productivity
- Non-Linux FOSS: Caffeine!
- Google's SwiftShader Released
- SuperTuxKart 0.9.2 Released
- Doing for User Space What We Did for Kernel Space
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide