This paper presents a unified set of abstractions and operations for
hardware devices, software processes, and media data in a distributed audio and video environment. These abstractions, which are provided through a middleware layer called Indiva, use a file system metaphor to access resources and high-level commands to simplify the development of Internet webcast and distributed collaboration control applications. The design and implementation of Indiva are described and examples are presented to illustrate the usefulness of the abstractions.
The JPEG compression standard is a popular image format. However, at high compression ratios JPEG compression, which uses block-transform coding, can produce blocking artifacts, or artificially introduced edges within the image. Several post-processing algorithms have been developed to remove these artifacts. This paper describes an implementation of a post-processing algorithm developed by Ramchandran, Chou, and Crouse (RCC) which is fast enough for real-time software-only video applications. The original implementation of the RCC algorithm involved calculating thresholds to identify artificial edges. These calculations proved too expensive for use in real-time software-only applications. We replaced these calculations with a linear scale approximating ideal threshold values based on a combination of peak signal-to-noise ratio calculations and subjective visual quality. The resulting filter implementation is available in the widely-deployed Open Mash streaming media toolkit.
This paper presents a system designed to automate the production of webcasts, the Virtual Director. It automates simple tasks such as control of recording equipment, stream broadcasting, and camera control. It also automates content decisions, such as which camera view to broadcast. Directors can specify the content decisions using an automation specification language. The Virtual Director also uses a question monitor service to automatically identify questions and move the cameras to show the audience member asking the question. We discuss the implementation of the Virtual Director and present the results of its use in the production of a university seminar series.
Live Internet streaming media programs, called webcasts, can adopt techniques developed by television to obtain higher quality. We have developed a general webcast production model composed of three stages (i.e., sources, broadcast, and transmission) and a tool, called the Director's Console (dc), to control live webcasts. The tool is one component of a distributed service architecture, which adapts to varying physical infrastructure and broadcast configurations.
The Internet Multicast Backbone (MBone) has seen tremendous growth during the past four years. For the past three and a half years, we have broadcast a weekly seminar on the MBone. The effort to set up and produce each broadcast has grown as we worked to improve the broadcasts and to support more services (e.g., on-demand playback, recording, video effect, etc.) This problem motivated us to develop a system to automate the tasks required to produce a broadcast. The motivation, requirements, and implementation of the system are presented.
Video effects play an important role in adding production value to video progress. The use of video effects with Internet Video sources, however, is still uncommon because traditional hardware-based solutions are poorly suited to the Internet environment. In previous work, we describe a parallel, software-only video effects system designed for Internet Video and explored the use of temporal parallelism. This paper explores the use of spatial parallelism. In particular, an intermediate semicompressed video format is described that was designed to exploit spatial parallelism, and performance measurements are reported on the use of this representation.
In this paper, we describe the design and implementation of a prototype software video production switcher, vps, that improves the quality of the content of MBone broadcasts. vps is modeled after the broadcast television industry's studio production switcher. It provides special effects processing to incorporate audience discussions, add titles and other information, and integrate stored videos into the presentation. vps is structured to work with other MBone conferencing tools. The ultimate goal is to automate the production of MBone broadcasts.
KEYWORDS: Video, Data modeling, Curium, Computer programming, Video processing, Process modeling, Multimedia, Adaptive control, Optical filters, Video compression
The design and performance of the Berkeley Continuous Media Toolkit (CMT) is described. CMT provides a programming environment for rapid development of continuous media applications. CMT overhead is measured in the context of a simple video playback application and is found to be only a few milliseconds per frame played. As a demonstration of CMT as a research infrastructure, an experiment comparing adaptive frame rate control policies is described.
Many image and video compression schemes perform the discrete cosine transform (DCT) to represent image data in frequency space. An analysis of a broad suite of images confirms previous findings that a Laplacian distribution can be used to model the luminance ac coefficients. This model is expanded and applied to color space (Cr/Cb) coefficients. In MPEG, the DCT is used to code interframe prediction error terms. The distribution of these coefficients is explored. Finally, the distribution model is applied to improve dynamic generation of quantization matrices.
Many algorithms have been proposed for detecting video
shot boundaries and classifying shot and shot transition types. Few published studies compare available algorithms, and those that do have looked at limited range of test material. This paper presents a comparison of several shot boundary detection and classification techniques and their variations including histograms, discrete cosine transform, motion vector, and block matching methods. The performance and ease of selecting good thresholds for these algorithms are evaluated based on a wide variety of video sequences with a good mix of transition types. Threshold selection requires a trade-off between recall and precision that must be guided by the target application.
Many algorithms have been proposed for detecting video shot boundaries and classifying shot and shot transition types. Few published studies compare available algorithms, and those that do have looked at limited range of test material. This paper presents a comparison of several shot boundary detection and classification techniques and their variations including histograms, discrete cosine transform, motion vector, and block matching methods. The performance and ease of selecting good thresholds for these algorithms are evaluated based on a wide variety of video sequences with a good mix of transition types. Threshold selection requires a trade-off between recall and precision that must be guided by the target application.
KEYWORDS: Computer programming, Video, Video compression, Algorithm development, Video coding, Video processing, Image quality standards, Video acceleration, Chromium, Image processing
In this paper we present an implementation of an MPEG1 encoder on the Intel Touchstone Delta and Intel Paragon parallel computers. We describe the unique aspects of mapping the algorithm onto the parallel machines and present several versions of the algorithms. We will show that I/O contention can be a bottleneck relative to performance. We will also describe how the Touchstone Delta and Paragon can be used to compress video sequences faster than real-time.
KEYWORDS: Video, Curium, Video processing, Adaptive control, Clocks, Software development, Video compression, Internet, Process control, Control systems
A software decoder for MPEG-1 video was integrated into a continuous media playback system that supports synchronized playing of audio and video data stored on a file server. The MPEG-1 video playback system supports forward and backward play at variable speeds and random positioning. Sending and receiving side heuristics are described that adapt to frame drops due to network load and the available decoding capability of the client workstation. A series of experiments show that the playback system adds a small overhead to the stand alone software decoder and that playback is smooth when all frames or very few frames can be decoded. Between these extremes, the system behaves reasonably but can still be improved.
Video-on-Demand systems have received a good deal of attention recently. Few studies, however, have addressed the problem of locating a video of interest in a large video database. This paper describes the design and implementation of a metadata database and query interface that attempts to solve this information retrieval problem.
KEYWORDS: Video, Databases, Distributed computing, Local area networks, Data storage, Computer programming, Multimedia, Video processing, Data archive systems, Nomenclature
The design of a distributed video-on-demand system that is suitable for large video libraries is described. The system is designed to store 1000s of hours of video material on tertiary storage devices. A video that a user wants to view is loaded onto a video file server close to the users desktop from where it can be played. The system manages the distributed cache of videos on the file servers and schedules load requests to the tertiary storage devices. The system also includes a metadata database, described in a companion paper, that the user can query to locate video material of interest. This paper describes the software architecture, storage organization, application protocols for locating and loading videos, and distributed cache management algorithm used by the system.
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