Region-based facial representation for real-time Action Units intensity detection across datasets

摘要

Most research on facial expressions recognition has focused on binary Action Units (AUs) detection, while graded changes in their intensity have rarely been considered. This paper proposes a method for the real-time detection of AUs intensity in terms of the Facial Action Coding System scale. It is grounded on a novel and robust anatomically based facial representation strategy, for which features are registered from a different region of interest depending on the AU considered. Real-time processing is achieved by combining Histogram of Gradients descriptors with linear kernel Support Vector Machines. Following this method, AU intensity detection models are built and validated through the DISFA database, outperforming previous approaches without real-time capabilities. An in-depth evaluation through three different databases (DISFA, BP4D and UNBC Shoulder-Pain) further demonstrates that the proposed method generalizes well across datasets. This study also brings insights about existing public corpora and their impact on AU intensity prediction.