  As communications are increasingly taking place virtually, the ability to
present well online is becoming an indispensable skill. Online speakers are
facing unique challenges in engaging with remote audiences. However, there has
been a lack of evidence-based analytical systems for people to comprehensively
evaluate online speeches and further discover possibilities for improvement.
This paper introduces SpeechMirror, a visual analytics system facilitating
reflection on a speech based on insights from a collection of online speeches.
The system estimates the impact of different speech techniques on effectiveness
and applies them to a speech to give users awareness of the performance of
speech techniques. A similarity recommendation approach based on speech factors
or script content supports guided exploration to expand knowledge of
presentation evidence and accelerate the discovery of speech delivery
possibilities. SpeechMirror provides intuitive visualizations and interactions
for users to understand speech factors. Among them, SpeechTwin, a novel
multimodal visual summary of speech, supports rapid understanding of critical
speech factors and comparison of different speech samples, and SpeechPlayer
augments the speech video by integrating visualization of the speaker's body
language with interaction, for focused analysis. The system utilizes
visualizations suited to the distinct nature of different speech factors for
user comprehension. The proposed system and visualization techniques were
evaluated with domain experts and amateurs, demonstrating usability for users
with low visualization literacy and its efficacy in assisting users to develop
insights for potential improvement.
