Real-time disk scheduling in a mixed-media file system

This paper presents our real-time disk scheduler called the Delta L scheduler, which optimizes unscheduled best-effort disk requests by giving priority to best-effort disk requests while meeting real-time request deadlines. Our scheduler tries to execute real-time disk requests as much as possible in the background. Only when real-time request deadlines are endangered, our scheduler gives priority to real-time disk requests. The Delta L disk scheduler is part of our mixed-media file system called Clockwise. An essential part of our work is extensive and detailed raw disk performance measurements. The Delta L disk scheduler for its real-time schedulability analysis and to decide whether scheduling a best-effort request before a real-time request violates real-time constraints uses these raw performance measurements. Further, a Clockwise off-line simulator uses the raw performance measurements where a number of different disk schedulers are compared. We compare the Delta L scheduler with a prioritizing Latest Start Time (LST) scheduler and non-prioritizing EDF scheduler. The Delta L scheduler is comparable to LST in achieving low latencies for best-effort requests under light to moderate real-time loads and better in achieving low latencies for best-effort requests for extreme real-time loads. The simulator is calibrated to an actual Clockwise. Clockwise runs on a 200MHz Pentium-Pro based PC with PCI bus, multiple SCSI controllers and disks on Linux 2.2.x and the Nemesis kernel. Clockwise performance is dictated by the hardware: all available bandwidth can be committed to real-time streams, provided hardware overloads do not occur

Synote: development of a Web-based tool for synchronized annotations

This paper discusses the development of a Web-based media annotation application named Synote, which addresses the important issue that while the whole of a multimedia resource on the Web can be easily bookmarked, searched, linked to and tagged, it is still difficult to search or associate notes or other resources with a certain part of a resource. Synote supports the creation of synchronized notes, bookmarks, tags, links, images and text captions. It is a freely available application that enables any user to make annotations in and search annotations to any fragment of a continuous multimedia resource in the most used browsers and operating systems. In the implementation, Synote categorized different media resources and synchronized them via time line. The presentation of synchronized resources makes full use of Web 2.0 AJAX technology to enrich interoperability for the user experience. Positive evaluation results about the performance, efficiency and effectiveness of Synote were returned when using it with students and teachers for a number of undergraduate courses