5,305 research outputs found
A generic framework for video understanding applied to group behavior recognition
This paper presents an approach to detect and track groups of people in
video-surveillance applications, and to automatically recognize their behavior.
This method keeps track of individuals moving together by maintaining a spacial
and temporal group coherence. First, people are individually detected and
tracked. Second, their trajectories are analyzed over a temporal window and
clustered using the Mean-Shift algorithm. A coherence value describes how well
a set of people can be described as a group. Furthermore, we propose a formal
event description language. The group events recognition approach is
successfully validated on 4 camera views from 3 datasets: an airport, a subway,
a shopping center corridor and an entrance hall.Comment: (20/03/2012
Using Variable Dwell Time to Accelerate Gaze-Based Web Browsing with Two-Step Selection
In order to avoid the "Midas Touch" problem, gaze-based interfaces for
selection often introduce a dwell time: a fixed amount of time the user must
fixate upon an object before it is selected. Past interfaces have used a
uniform dwell time across all objects. Here, we propose a gaze-based browser
using a two-step selection policy with variable dwell time. In the first step,
a command, e.g. "back" or "select", is chosen from a menu using a dwell time
that is constant across the different commands. In the second step, if the
"select" command is chosen, the user selects a hyperlink using a dwell time
that varies between different hyperlinks. We assign shorter dwell times to more
likely hyperlinks and longer dwell times to less likely hyperlinks. In order to
infer the likelihood each hyperlink will be selected, we have developed a
probabilistic model of natural gaze behavior while surfing the web. We have
evaluated a number of heuristic and probabilistic methods for varying the dwell
times using both simulation and experiment. Our results demonstrate that
varying dwell time improves the user experience in comparison with fixed dwell
time, resulting in fewer errors and increased speed. While all of the methods
for varying dwell time resulted in improved performance, the probabilistic
models yielded much greater gains than the simple heuristics. The best
performing model reduces error rate by 50% compared to 100ms uniform dwell time
while maintaining a similar response time. It reduces response time by 60%
compared to 300ms uniform dwell time while maintaining a similar error rate.Comment: This is an Accepted Manuscript of an article published by Taylor &
Francis in the International Journal of Human-Computer Interaction on 30
March, 2018, available online:
http://www.tandfonline.com/10.1080/10447318.2018.1452351 . For an eprint of
the final published article, please access:
https://www.tandfonline.com/eprint/T9d4cNwwRUqXPPiZYm8Z/ful
Video browsing interfaces and applications: a review
We present a comprehensive review of the state of the art in video browsing and retrieval systems, with special emphasis on interfaces and applications. There has been a significant increase in activity (e.g., storage, retrieval, and sharing) employing video data in the past decade, both for personal and professional use. The ever-growing amount of video content available for human consumption and the inherent characteristics of video data—which, if presented in its raw format, is rather unwieldy and costly—have become driving forces for the development of more effective solutions to present video contents and allow rich user interaction. As a result, there are many contemporary research efforts toward developing better video browsing solutions, which we summarize. We review more than 40 different video browsing and retrieval interfaces and classify them into three groups: applications that use video-player-like interaction, video retrieval applications, and browsing solutions based on video surrogates. For each category, we present a summary of existing work, highlight the technical aspects of each solution, and compare them against each other
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