Scalable Media Research Articles

Quality Control for Scalable Media Processing Applications

Many media processing applications create a load that varies significantly over time. Hence, if such an application is assigned a lower processing-time budget than needed in its worst-case load sit...

On network CoProcessors for scalable, predictable media services

This paper presents the embedded realization and experimental evaluation of a media stream scheduler on network interface (NI) CoProcessor boards. When using media frames as scheduling units, the scheduler is able to operate in real-time on streams traversing the CoProcessor, resulting in its ability to stream video to remote clients at real-time rates. This paper presents a detailed evaluation of the effects of placing application or kernel-level functionality, like packet scheduling on NIs, rather than the host machines to which they are attached. The main benefits of such placement are: 1) that traffic is eliminated from the host bus and memory subsystem, thereby allowing increased host CPU utilization for other tasks, and 2) that NI-based scheduling is immune to host-CPU loading, unlike host-based media schedulers that are easily affected even by transient load conditions. An outcome of this work is a proposed cluster architecture for building scalable media servers by distributing schedulers and media stream producers across the multiple NIs used by a single server and by clustering a number of such servers using commodity network hardware and software.

Dynamic class-based queue management for scalable media servers

Real-time media servers are becoming increasingly important due to the rapid transition of the Internet from text- and graphics-based applications to multimedia-driven environments. In order to meet these ever increasing demands, real-time media servers are responsible for supporting a large number of clients with a heterogeneous mix of quality of service (QoS) requirements. In this paper, we propose a dynamic class-based queue management scheme that effectively captures the trade-off between scalability and QoS granularity in a media server. We examine the adaptiveness of the scheme and its integration with the existing schedulers. Finally, we evaluate the effectiveness of the proposed scheme through extensive simulation studies.

A Scalable Media Processor Based Image Data Path for the Xerox DocuSP Platform

The Xerox Document Services Platform (DocuSP) is the Xerox Digital Front End platform for production products. DocuSP supports over 26 different production engines that include monochrome, color, cut sheet, and continuous feed products. In particular DocuSP is one of the Digital Front Ends for the Xerox iGen3 Digital Press. This talk will describe some unique technologies in the DocuSP DFE that enable high performance printing at 100 pages per minute in full color. Unique to this controller is the concept of a scalable performance, “soft” image data path, implemented in array of low cost media processors from Equator Technologies that provide the image processing required for full performance printing on iGen3. This allows DocuSP to be an agile platform to support new imaging features without the overhead of lengthy hardware development.

Quality of service evaluations of multicast streaming protocols

Recently proposed scalable on-demand streaming protocols have previously been evaluated using a system cost measure termed the "required server bandwidth". For the scalable protocols that provide immediate service to each client when the server is not overloaded, this paper develops simple analytic models to evaluate two client-oriented quality of service metrics, namely (1) the mean client waiting time in systems where clients are willing to wait if a (well-provisioned) server is temporarily overloaded, and (2) the fraction of clients who balk (i.e., leave without receiving their requested media content) in systems where the clients will tolerate no or only very low service delays during a temporary overload. The models include novel approximate MVA techniques that appear to extend the range of applicability of customized AMVA to include questions focussed on state probabilities rather than on mean values, and to systems in which the operating points of interest do not include substantial client queues. For example, the new AMVA models accurately estimate the server bandwidth needed to achieve a balking rate as low as one in ten thousand. The analytic models can easily be applied to determine the server bandwidth needed for a given number of media files, anticipated total client request rate and file access frequencies, and target balking rate or mean wait. Results show that (a) scalable media servers that are configured with the "required server bandwidth" defined in previous work have low mean wait but may have unacceptably high client balking rates (i.e., greater than one in twenty), (b) for high to moderate client load, only a 10 - 50% increase in the previously defined required server bandwidth is needed to achieve a very low balking rate (e.g., one in ten thousand), and (c) media server performance (either mean wait or balking rate) degrades rapidly if the actual client load is more than 10% greater than the anticipated load.

Design of Scalable Continuous Media Servers

Multimedia applications place high demands for quality-of-service (QoS), performance, and reliability on systems. These stringent requirements make design of cost-effective and scalable systems difficult. Therefore efficient adaptive and dynamic resource management techniques in conjunction with data placement techniques can be of great help in improving performance, scalability, and reliability of such systems. This is the focus of our paper.

On packetization of embedded multimedia bitstreams

We study the problem of packetizing embedded multimedia bitstreams to improve the error resilience of source (compression) codes. This problem is important because of the increasing popularity of embedded compression methodology and its suitability for scalable streaming media over IP or/and mobile IP. We study various packetization schemes against packet erasure at both low and high bit rates. Maximizing packetization efficiency for embedded bitstreams is formulated as a discrete optimization problem and globally optimal packetization (OP) algorithms are proposed under different settings. Suboptimal packetization algorithms are also devised to reduce the complexity of the OP algorithms. In order to assess their effectiveness, the proposed packetization algorithms are used to packetize embedded image and video bitstreams with simulated packet loss. Experimental results show that our OP algorithms slightly outperforms suboptimal ones. In addition to confirming the superiority of the OP algorithms, these results also provide justification of heuristic packetization methods published in the literature.

QoS adaptive transports: delivering scalable media to the desktop

By trading off temporal and spatial quality with available bandwidth, or manipulating the payout time of continuous media in response to variation in delay, audio and video flows can be made to adapt to fluctuating network conditions with minimal perceptual distortion. The authors describe the implementation of an adaptive transport system that incorporates a quality of service (QoS) oriented application programming interface (API) and a range of QoS mechanisms that best assist multimedia applications in adapting to fluctuations in the delivered network QoS. The system, which is an instantiation of the transport and network layers of a QoS architecture, is implemented in a multi-ATM switch network environment with Linux-based PC end systems and continuous media file servers. A performance evaluation of the system configured to support a video-on-demand application scenario is presented and discussed. A novel aspect of the system is the implementation of a "QoS adaptation" algorithm which allows applications to delegate to the transport system responsibility for augmenting or reducing the perceptual quality of video and audio flows when network resource increases or decreases, respectively.