Micro-Expression Recognition Enhanced by Macro-Expression from Spatial-Temporal Domain

Facial micro-expression recognition has attracted much attention due to its objectiveness to reveal the true emotion of a person. However, the limited micro-expression datasets have posed a great challenge to train a high performance micro-expression classifier. Since micro-expression and macroexpression share some similarities in both spatial and temporal facial behavior patterns, we propose a macro-to-micro transformation framework for micro-expression recognition. Specifically, we first pretrain two-stream baseline model from microexpression data and macro-expression data respectively, named MiNet and MaNet. Then, we introduce two auxiliary tasks to align the spatial and temporal features learned from micro-expression data and macro-expression data. In spatial domain, we introduce a domain discriminator to align the features of MiNet and MaNet. In temporal domain, we introduce relation classifier to predict the correct relation for temporal features from MaNet and MiNet. Finally, we propose contrastive loss to encourage the MiNet to give closely aligned features to all entries from the same class in each instance. Experiments on three benchmark databases demonstrate the superiority of the proposed method.