  Appropriate gestures can enhance message delivery and audience engagement in
both daily communication and public presentations. In this paper, we contribute
a visual analytic approach that assists professional public speaking coaches in
improving their practice of gesture training through analyzing presentation
videos. Manually checking and exploring gesture usage in the presentation
videos is often tedious and time-consuming. There lacks an efficient method to
help users conduct gesture exploration, which is challenging due to the
intrinsically temporal evolution of gestures and their complex correlation to
speech content. In this paper, we propose GestureLens, a visual analytics
system to facilitate gesture-based and content-based exploration of gesture
usage in presentation videos. Specifically, the exploration view enables users
to obtain a quick overview of the spatial and temporal distributions of
gestures. The dynamic hand movements are firstly aggregated through a heatmap
in the gesture space for uncovering spatial patterns, and then decomposed into
two mutually perpendicular timelines for revealing temporal patterns. The
relation view allows users to explicitly explore the correlation between speech
content and gestures by enabling linked analysis and intuitive glyph designs.
The video view and dynamic view show the context and overall dynamic movement
of the selected gestures, respectively. Two usage scenarios and expert
interviews with professional presentation coaches demonstrate the effectiveness
and usefulness of GestureLens in facilitating gesture exploration and analysis
of presentation videos.
