2888187
Asynchronous collaboration around multimedia and its application to on-demand training
Multimedia content is a central component of on-demand training and education delivered over the World Wide Web. Supporting asynchronous collaboration around educational multimedia is a key requirement for making the online educational environment effective. A multimedia annotation system tightly integrated with email provides a powerful platform on which to base such functionality. Building on our earlier work with multimedia annotations, we present user interface and system extensions to support asynchronous collaboration for on-demand training. We report results from a study of the effectiveness of the system, including student experience, instructor experience, and user interface appropriateness. Overall, the student experience was positive: they appreciated the flexibility of on-demand delivery and benefited from the collaborative features.
8300930
Browsing digital video
Video in digital format played on programmable devices presents opportunities for significantly enhancing the user's viewing experience. For example, time compression and pause removal can shorten the viewing time for a video, textual and visual indices can allow personalized navigation through the content, and random-access digital storage allows instantaneous seeks into the content. To understand user behavior when such capabilities are available, we built a software video browsing application that combines many such features. We present results from a user study where users browsed video in six different categories: classroom lectures, conference presentations, entertainment shows, news, sports, and travel. Our results show that the most frequently used features were time compression, pause removal, and navigation using shot boundaries. Also, the behavior was different depending on the content type, and we present a classification. Finally, the users found the browser to be very useful. Two main reasons were: i) the ability to save time and ii) the feeling of control over what content they watched.
11065544
Profile-driven energy reduction in network-on-chips
Reducing energy consumption of a Network-on-Chip (NoC) is a critical design goal, especially for power-constrained embedded systems.In response, prior research has proposed several circuit/architectural level mechanisms to reduce NoC power consumption. This paper considers the problem from a different perspective and demonstrates that compiler analysis can be very helpful for enhancing the effectiveness of a hardware-based link power management mechanism by increasing the duration of communication links' idle periods. The proposed profile-based approach achieves its goal by maximizing the communication link reuse through compiler-directed, static message re-routing. That is, it clusters the required data communications into a small set of communication links at any given time, which increases the idle periods for the remaining communication links in the network. This helps hardware shut down more communication links and their corresponding buffers to reduce leakage power. The current experimental evaluation, with twelve data-intensive embedded applications, shows that the proposed profile-driven compiler approach reduces leakage energy by more than 35% (on average) as compared to a pure hardware-based link power management scheme.
13530819
Exploiting last idle periods of links for network power management
Network power optimization is becoming increasingly important as the sizes of the data manipulated by parallel applications and the complexity of inter-processor data communications are continuously increasing. Several hardware-based schemes have been proposed in the past for reducing network power consumption, either by turning off unused communication links or by lowering voltage/frequency in links with low usage. While the prior research shows that these schemes can be effective in certain cases, they share the common drawback of not being able to predict the link active and idle times very accurately. This paper, instead, proposes a compiler-based scheme that determines the last use of communication links at each loop nest and inserts explicit link turn-off calls in the application source. Specifically, for each loop nest, the compiler inserts a turn-off call per communication link. Each turned-off link is reactivated upon the next access to it. We automated this approach within a parallelizing compiler and applied it to eight array-intensive embedded applications.
8490960
Proof-Infused Streams: Enabling Authentication of Sliding Window Queries On Streams
As computer systems are essential components of many critical commercial services, the need for secure online transactions is now becoming evident. The demand for such applications, as the market grows, exceeds the capacity of individual businesses to provide fast and reliable services, making outsourcing technologies a key player in alleviating issues of scale. Consider a stock broker that needs to provide a real-time stock trading monitoring service to clients. Since the cost of multicasting this information to a large audience might become prohibitive, the broker could outsource the stock feed to third-party providers, who are in turn responsible for forwarding the appropriate sub-feed to clients. Evidently, in critical applications the integrity of the third-party should not be taken for granted. In this work we study a variety of authentication algorithms for selection and aggregation queries over sliding windows. Our algorithms enable the end-users to prove that the results provided by the third-party are correct, i.e., equal to the results that would have been computed by the original provider. Our solutions are based on Merkle hash trees over a forest of space partitioning data structures, and try to leverage key features, like update, query, signing, and authentication costs. We present detailed theoretical analysis for our solutions and empirically evaluate the proposed techniques.
8615414
Collaborative distributed virtual sculpting
A lot of effort is now being put into developing collaborative distributed virtual environments. However very few projects address collaborative virtual sculpting in which the shapes of the target objects are likely changing continuously. Some major issues including user interaction, data transmission, concurrent object editing by multiple clients and rendering of deforming objects must be addressed in a real-time context. We propose a framework for collaborative virtual sculpting in a distributed virtual environment. The system is based on a hybrid model which merges the client-server and the peer-to-peer architectures to allow fast data replication. To support real-time deformation and rendering of deformable objects, we model each of these objects using NURBS surfaces and render them using the real-time deformable NURBS rendering method that we have developed. We present a data structure for the transmission of these deformable objects. We also introduce the idea of editing region and the corresponding locking mechanism for simultaneous editing of the same object by multiple clients. Toward the end of the paper we show some performance results of the prototype system.
9337355
Weather forecasting: predicting performance for streaming video over wireless LANs
The growth of wireless LANs has brought the expectation for high-bitrate streaming video to wireless PCs. However, it remains unclear how wireless channel characteristics impact the quality of streaming video sent over wireless LANs. This paper presents results from experiments that stream commercial video over a wireless campus network. By analyzing the streaming video quality and capturing wireless LAN characteristics across network and wireless link layers, "weather forecasts" are created such that selected wireless LAN performance indicators might be used to predict the streaming video quality. Furthermore, a quantified measurement of accuracy is presented to evaluate the effectiveness of individual weather forecasts. The paper evaluates six distinct weather forecasts four different streaming configurations including TCP and UDP streaming, and single and multiple-level encoded videos. The results show that the wireless Received Signal Strength Indicator (RSSI) and average wireless link capacity are the most accurate indicators to predict the performance of streaming video over wireless LANs. The weather forecast philosophy can be beneficial for adapting video streaming in wireless LAN environments.