ABPN: Apex and Boundary Perception Network for Micro- and Macro-Expression Spotting

Recently, Micro expression~(ME) has achieved remarkable progress in a wide range of applications, since it's an involuntary facial expression that reflects personal psychological state truly. In the procedure of ME analysis, spotting ME is an essential step, and is non trivial to be detected from a long interval video because of the short duration and low intensity issues. To alleviate this problem, in this paper, we propose a novel Micro- and Macro-Expression~(MaE) Spotting framework based on Apex and Boundary Perception Network~(ABPN), which mainly consists of three parts, i.e., video encoding module ~(VEM), probability evaluation module~(PEM), and expression proposal generation module~(EPGM). Firstly, we adopt Main Directional Mean Optical Flow (MDMO) algorithm and calculate optical flow differences to extract facial motion features in VEM, which can alleviate the impact of head movement and other areas of the face on ME spotting. Then, we extract temporal features with one-dimension convolutional layers and introduce PEM to infer the auxiliary probability that each frame belongs to an apex or boundary frame. With these frame-level auxiliary probabilities, the EPGM further combines the frames from different categories to generate expression proposals for the accurate localization. Besides, we conduct comprehensive experiments on MEGC2022 spotting task, and demonstrate that our proposed method achieves significant improvement with the comparison of state-of-the-art baselines on rm CAS(ME)2 and SAMM-LV datasets. The implemented code is also publicly available at https://github.com/wenhaocold/USTC_ME_Spotting.