Parallel Queries for Human-Object Interaction Detection

Human-Object Interaction (HOI) Detection requires localizing a pair of humans and objects. Recent transformer-based methods leverage the query embeddings to represent the entire HOI instances. The target embeddings after decoding are used to represent the object and human characteristics at the same time. However, it is ambiguous to use the highly integrated embeddings to localize the human and object simultaneously. To address this problem, we split the detection decoding process into subject decoding and object decoding to detect the humans and objects in parallel. Our proposed method, Parallel Query Network (PQNet) uses two transformer decoders to decode the subject embeddings and object embeddings in parallel, and a novel verb decoder is used to fuse the representation from the detection decoding and predict the interaction. The attention mechanisms in the verb decoder consist of the attention between human and object embeddings and the attention between the fused embeddings and global semantic features. As the transformer architecture maintains the permutation of the input query embeddings, the paired boxes of humans and objects are directly predicted by feed-forward networks. With the full usage of the object detection part, our proposed architecture outperforms the state-of-the-art baseline method with half of the training epochs.