This paper conducts a performance analysis of two popular private blockchain platforms, Hyperledger Fabric and Ethereum (private deployment), to assess the performance and limitations of these state-of-the-art platforms. Blockchain, a decentralized transaction and data management technology, is said to be the technology that will have similar impacts as the Internet had on people's lives. Many industries have become interested in adopting blockchain in their IT systems, but scalability is an often- cited concern of current blockchain technology. Therefore, the goals of this preliminary performance analysis are twofold. First, a methodology for evaluating a blockchain platform is developed. Second, the analysis results are presented to inform practitioners in making decisions regarding adoption of blockchain technology in their IT systems. The experimental results, based on varying number of transactions, show that Hyperledger Fabric consistently outperforms Ethereum across all evaluation metrics which are execution time, latency and throughput. Additionally, both platforms are still not competitive with current database systems in term of performances in high workload scenarios.

Video tutorials provide a convenient means for novices to learn new software applications. Unfortunately, staying in sync with a video while trying to use the target application at the same time requires users to repeatedly switch from the application to the video to pause or scrub backwards to replay missed steps. We present Pause-and-Play, a system that helps users work along with existing video tutorials. Pause-and-Play detects important events in the video and links them with corresponding events in the target application as the user tries to replicate the depicted procedure. This linking allows our system to automatically pause and play the video to stay in sync with the user. Pause-and-Play also supports convenient video navigation controls that are accessible from within the target application and allow the user to easily replay portions of the video without switching focus out of the application. Finally, since our system uses computer vision to detect events in existing videos and leverages application scripting APIs to obtain real time usage traces, our approach is largely independent of the specific target application and does not require access or modifications to application source code. We have implemented Pause-and-Play for two target applications, Google SketchUp and Adobe Photoshop, and we report on a user study that shows our system improves the user experience of working with video tutorials.

When browsing a long video using a traditional timeline slider control, its effectiveness and precision degrade as a video's length grows. When browsing videos with more frames than pixels in the slider, aside from some frames being inaccessible, scrolling actions cause sudden jumps in a video's continuity as well as video frames to flash by too fast for one to assess the content. We propose a content-aware dynamic timeline control that is designed to overcome these limitations. Our timeline control decouples video speed and playback speed, and leverages video content analysis to allow salient shots to be presented at an intelligible speed. Our control also takes advantage of previous work on elastic sliders, which allows us to produce an accurate navigation control.

Watching a long unedited video is usually a boring experience. In this paper we examine a particular subset of videos, tour videos, in which the video is captured by walking about with a running camera with the goal of conveying the essence of some place. We present a system that makes the process of sharing and watching a long tour video easier, less boring, and more informative. To achieve this, we augment the tour video with a map-based storyboard, where the tour path is reconstructed, and coherent shots at different locations are directly visualized on the map. This allows the viewer to navigate the video in the joint location-time space. To create such a storyboard we employ an automatic pre-processing component to parse the video into coherent shots, and an authoring tool to enable the user to tie the shots with landmarks on the map. The browser-based viewing tool allows users to navigate the video in a variety of creative modes with a rich set of controls, giving each viewer a unique, personal viewing experience. Informal evaluation shows that our approach works well for tour videos compared with conventional media players.