Roger Midtstraum

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Video servers are important for applications which make use of digital video. The video servers should provide better functionality than most of today's video servers offer, – e.g., support of flexible and instant user interactions, delivery of multiple video formats and support of virtual video documents. In this paper we discuss the requirements that(More)
We present a technique to prevent cheating in online-games. Our approach prevents both, modification of game-clients, and access to sensitive information in the game-clients' memory. It allows game-servers to detect cheating attempts. The mechanisms in our solution are orthogonal to the game-related mechanisms, allowing to clearly separate security-related(More)
In this chapter we will discuss issues related to searching and browsing a shared video database. The discussion will be founded on a review of characteristics of video information and video database applications, and we will discuss requirements to be fulllled by video databases in shared environments. The issues that will be discussed include video(More)
In traditional video archives, video data are stored on analogue video tapes while meta-data, such as textual descriptions of the contents of the video tapes, are stored and handled digitally by computers. In a fully digital video archive, both video data and meta-data are managed by computers and, thus, more powerful tools can be developed. In this paper,(More)
Audio and video data represent streams of data with inherent temporal properties. In this paper we consider a video database as a collection of partial ordered sets where temporal relationships exist between elements from the same video stream. Video production introduces dependencies between diierent time coordinate systems. In this paper we give a formal(More)
This paper describes the VideoSTAR experimental database system that is being designed to support video applications in sharing and reusing video data and meta-data. VideoSTAR provides four diierent repositories: for media les, virtual documents, video structures, and video annotations/user indexes. It also provides a generic video data model relating data(More)
When a serpentine tape drive is used as a slow random access device, the I/O performance can be substantially improved by clever reordering of the I/O requests. This kind of reordering relies on a scheduling algorithm and a model of the access time. In this paper, we propose a low-cost access time model for serpentine tape drives, which is not a trivial(More)
This paper presents a general model for estimating access times of serpentine tape drives. The model is used to schedule I/O requests in order to minimize the total access time. We propose a new scheduling algorithm, Multi-Pass Scan Star (MPScan*), which makes good utilization of the streaming capability of the tape drive and avoids the pitfalls of naive(More)
This paper discusses scheduling of random I/O requests for multimedia data stored on magnetic tape using serpen-tine data layout. Results from simulations and real experiments show that substantial improvements of retrieval performance can be achieved by proper I/O scheduling. A new algorithm, Multi-Pass Scan Star (MPScan*), is presented and shown to give(More)