On the role of Lip Articulation in Visual Speech Perception
This work addresses the problem of improving subjective animation quality for realistic character animation, though it is incremental as it focuses on understanding perception rather than developing new methods.
The study investigated how the degree of lip articulation (under-articulated vs. over-articulated) affects human perception of quality in lip motion generated from speech, finding that viewers consistently prefer over-articulated lip motion across different speakers and embodiments.
Generating realistic lip motion from audio to simulate speech production is critical for driving natural character animation. Previous research has shown that traditional metrics used to optimize and assess models for generating lip motion from speech are not a good indicator of subjective opinion of animation quality. Devising metrics that align with subjective opinion first requires understanding what impacts human perception of quality. In this work, we focus on the degree of articulation and run a series of experiments to study how articulation strength impacts human perception of lip motion accompanying speech. Specifically, we study how increasing under-articulated (dampened) and over-articulated (exaggerated) lip motion affects human perception of quality. We examine the impact of articulation strength on human perception when considering only lip motion, where viewers are presented with talking faces represented by landmarks, and in the context of embodied characters, where viewers are presented with photo-realistic videos. Our results show that viewers prefer over-articulated lip motion consistently more than under-articulated lip motion and that this preference generalizes across different speakers and embodiments.