  Emotions play a key role in human communication and public presentations.
Human emotions are usually expressed through multiple modalities. Therefore,
exploring multimodal emotions and their coherence is of great value for
understanding emotional expressions in presentations and improving presentation
skills. However, manually watching and studying presentation videos is often
tedious and time-consuming. There is a lack of tool support to help conduct an
efficient and in-depth multi-level analysis. Thus, in this paper, we introduce
EmoCo, an interactive visual analytics system to facilitate efficient analysis
of emotion coherence across facial, text, and audio modalities in presentation
videos. Our visualization system features a channel coherence view and a
sentence clustering view that together enable users to obtain a quick overview
of emotion coherence and its temporal evolution. In addition, a detail view and
word view enable detailed exploration and comparison from the sentence level
and word level, respectively. We thoroughly evaluate the proposed system and
visualization techniques through two usage scenarios based on TED Talk videos
and interviews with two domain experts. The results demonstrate the
effectiveness of our system in gaining insights into emotion coherence in
presentations.
