Jacob Wobbrock
University of Washington, Information School, Faculty Member
Mobile video is becoming a mainstream method of communication. Deaf and hard-of-hearing people benefit the most because mobile video enables real-time sign language communication. However, mobile video quality can become unintelligible... more
Mobile video is becoming a mainstream method of communication. Deaf and hard-of-hearing people benefit the most because mobile video enables real-time sign language communication. However, mobile video quality can become unintelligible due to high video transmission rates causing network congestion and delayed video. My dissertation research focuses on making mobile sign language video more accessible and affordable without relying on higher cellular network capacity while extending cellphone battery life. I am investigating how much frame rate and bitrate of sign language video can be reduced before compromising video intelligibility. Web and laboratory studies are conducted to evaluate perceived intelligibility of video transmitted at low frame rates and bitrates. I also propose the Human Signal Intelligibility Model (HSIM) addressing the lack of a universal model to base video intelligibility evaluations.
The current recommended video transmission standards, Telecommunication Standardization Sector (ITU-T) Q.26/16, of 25 frames per second at 100 kilobits per second or higher make mobile sign language video communication less accessible... more
The current recommended video transmission standards, Telecommunication Standardization Sector (ITU-T) Q.26/16, of 25 frames per second at 100 kilobits per second or higher make mobile sign language video communication less accessible than it could be with a more relaxed standard. The current bandwidth requirements are high enough that network congestion may occur, causing delays or lost information. In addition, limited data plans may cause higher cost to video communication users. To increase the accessibility and affordability of video communication, we explore a relaxed standard for video transmission using lower frame rates and bitrates. We introduce a novel measure, the Human Signal Intelligibility Model, to accomplish this. We propose web and laboratory studies to validate lower bounds on frame rates and bitrates for sign language communication on small mobile devices. Author
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Research Interests: Computer Science, Human Computer Interaction, Usability, Collaboration, Human Factors in Computing Systems, and 11 moreWeb usability, Usability Engineering, Usability Evaluation, Graphic User Interface Design, Educational Change, General Terms, Domain Specificity, Domains, Cognitive Walkthrough, Computer Human Interaction, and Model Complexity
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A study of small groups collaborating at an interactive tabletop was conducted. Group discussions were coded according to the type and quality of social regulation processes used. Episodes of high and low quality social regulation were... more
A study of small groups collaborating at an interactive tabletop was conducted. Group discussions were coded according to the type and quality of social regulation processes used. Episodes of high and low quality social regulation were then matched with the software logs to identify patterns of interaction associated with quality of social regulation. A key finding is that instances of low-quality social regulation were characterized by more than twice as much interaction with the software as high-quality instances.
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September 3-4, 2007 Leicester, UK Not Typing but Writing: Eye-based Text Entry Using Letter-like Gestures Jacob O. Wobbrock, James Rubinstein, Michael Sawyer, and Andrew T. Duchowski The Information School University of Washington... more
September 3-4, 2007 Leicester, UK Not Typing but Writing: Eye-based Text Entry Using Letter-like Gestures Jacob O. Wobbrock, James Rubinstein, Michael Sawyer, and Andrew T. Duchowski The Information School University of Washington Seattle, WA 98195 USA wobbrock@u.washington.edu Department of Psychology Department of Industrial Engineering School of Computing Clemson University Clemson, SC USA 29634 {jrubins, msawyer, andrewd}@clemson.edu
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For over six decades, Fitts's law (1954) has been utilized by researchers to quantify human pointing performance in terms of "throughput, " a combined speed-accuracy measure of aimed movement efficiency. Throughput... more
For over six decades, Fitts's law (1954) has been utilized by researchers to quantify human pointing performance in terms of "throughput, " a combined speed-accuracy measure of aimed movement efficiency. Throughput measurements are commonly used to evaluate pointing techniques and devices, helping to inform software and hardware developments. Although Fitts's law has been used extensively in HCI and beyond, its test-retest reliability, both in terms of throughput and model ft, from one session to the next, is still unexplored. Additionally, despite the fact that prior work has shown that Fitts's law provides good model fits, with Pearson correlation coefficients commonly at r =.90 or above, the model fit-ness of Fitts's law has not been thoroughly investigated for people who exhibit limited fine motor function in their dominant hand. To fill these gaps, we conducted a study with 21 participants with limited fine motor function and 34 participants without su...
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Data not suitable for classic parametric statistical analyses arise frequently in human–computer interaction studies. Various nonparametric statistical procedures are appropriate and advantageous when used properly. This chapter organizes... more
Data not suitable for classic parametric statistical analyses arise frequently in human–computer interaction studies. Various nonparametric statistical procedures are appropriate and advantageous when used properly. This chapter organizes and illustrates multiple nonparametric procedures, contrasting them with their parametric counterparts. Guidance is given for when to use nonparametric analyses and how to interpret and report their results.
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Mobile sign language video conversations can become unintelligible if high video transmission rates cause network congestion and delayed video. In an effort to understand the perceived lower limits of intelligible sign language video... more
Mobile sign language video conversations can become unintelligible if high video transmission rates cause network congestion and delayed video. In an effort to understand the perceived lower limits of intelligible sign language video intended for mobile communication, we evaluated sign language video transmitted at four low frame rates (1, 5, 10, and 15 frames per second [fps]) and four low fixed bit rates (15, 30, 60, and 120 kilobits per second [kbps]) at a constant spatial resolution of 320 × 240 pixels. We discovered an “intelligibility ceiling effect,” in which increasing the frame rate above 10fps did not improve perceived intelligibility, and increasing the bit rate above 60kbps produced diminishing returns. Given the study parameters, our findings suggest that relaxing the recommended frame rate and bit rate to 10fps at 60kbps will provide intelligible video conversations while reducing total bandwidth consumption to 25% of the ITU-T standard (at least 25fps and 100kbps). As...
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This paper describes the author's dissertation research on designing, implementing, and evaluating the Edge Write text entry method. The goal of this research is to develop a method that is highly "robust," remaining... more
This paper describes the author's dissertation research on designing, implementing, and evaluating the Edge Write text entry method. The goal of this research is to develop a method that is highly "robust," remaining accessible and accurate across a variety of devices, abilities, circumstances, and constraints. Edge Write is particularly aimed at users with motor impairments and able-bodied users "on the go." To date, this research has resulted in versions of Edge Write for PDAs, touchpads, displacement joysticks, isometric joysticks, trackballs, 4-keys, and more, all of which use the same Edge Write alphabet and concepts. The stylus version, for instance, has been shown to be significantly more accurate than Graffiti for both able-bodied and motor-impaired users. Similarly, the trackball version has been shown to be better than on-screen keyboards for some people who use trackballs due to motor impairments. This paper discusses these and other achievements, ...
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Measures of Text Entry Performance Jacob O. Wobbrock University of Washington, Seattle, WA, USA 3.1 INTRODUCTION When people encounter a new text entry method, the first question they usually ask is, How fast is it? Although speed is a... more
Measures of Text Entry Performance Jacob O. Wobbrock University of Washington, Seattle, WA, USA 3.1 INTRODUCTION When people encounter a new text entry method, the first question they usually ask is, How fast is it? Although speed is a key feature of any text entry ...
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Power wheelchair joysticks have been used to control a mouse cursor on desktop computers, but they offer no integrated text entry solution, confining users to point-and-click or point-and-dwell with on-screen keyboards. But on-screen... more
Power wheelchair joysticks have been used to control a mouse cursor on desktop computers, but they offer no integrated text entry solution, confining users to point-and-click or point-and-dwell with on-screen keyboards. But on-screen keyboards reduce useful screen real-estate, exacerbate the need for frequent window management, and impose a second focus of attention. By contrast, we present two integrated gestural text entry methods designed for use from power wheelchairs: one for joysticks and the other for touchpads. Both techniques are adaptations of EdgeWrite, originally a stylus-based unistroke method designed for people with tremor. In a preliminary study of 7 power wheelchair users, we found that touchpad EdgeWrite was faster than joystick WiVik, and joystick EdgeWrite was only slightly slower after minimal practice. These findings reflect "walk up and use"-ability and warrant further investigation into extended use.