Video Action Transformer Network

We introduce the Action Transformer model for recognizing and localizing human actions in video clips. We repurpose a Transformer-style architecture to aggregate features from the spatiotemporal context around the person whose actions we are trying to classify. We show that by using high-resolution, person-specific, class-agnostic queries, the model spontaneously learns to track individual people and to pick up on semantic context from the actions of others. Additionally its attention mechanism learns to emphasize hands and faces, which are often crucial to discriminate an action - all without explicit supervision other than boxes and class labels. We train and test our Action Transformer network on the Atomic Visual Actions (AVA) dataset, outperforming the state-of-the-art by a significant margin using only raw RGB frames as input.

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Results from the Paper

Task Dataset Model Metric Name Metric Value Global Rank Result Benchmark
Action Recognition AVA v2.1 I3D Tx HighRes mAP (Val) 27.6 # 6
GFlops 39.6 # 2
Params (M) 19.3 # 1
Action Recognition AVA v2.1 I3D I3D mAP (Val) 23.4 # 10
GFlops 6.5 # 1
Params (M) 16.2 # 2