Papers › Im2Flow: Motion Hallucination from Static Images for Action Recognition

Im2Flow: Motion Hallucination from Static Images for Action Recognition

12 Dec 2017CVPR 2018 6arXiv:1712.04109archive 2025-07-28

Ruohan Gao, Bo Xiong, Kristen Grauman

Existing methods to recognize actions in static images take the images at their face value, learning the appearances---objects, scenes, and body poses---that distinguish each action class. However, such models are deprived of the rich dynamic structure and motions that also define human activity. We propose an approach that hallucinates the unobserved future motion implied by a single snapshot to help static-image action recognition. The key idea is to learn a prior over short-term dynamics from thousands of unlabeled videos, infer the anticipated optical flow on novel static images, and then train discriminative models that exploit both streams of information. Our main contributions are twofold. First, we devise an encoder-decoder convolutional neural network and a novel optical flow encoding that can translate a static image into an accurate flow map. Second, we show the power of hallucinated flow for recognition, successfully transferring the learned motion into a standard two-stream network for activity recognition. On seven datasets, we demonstrate the power of the approach. It not only achieves state-of-the-art accuracy for dense optical flow prediction, but also consistently enhances recognition of actions and dynamic scenes.

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rhgao/Deep-MIML-Network mentioned on GitHubpytorch report
rhgao/Im2Flow mentioned on GitHubtorch report
rhgao/separating-object-sounds mentioned on GitHubpytorch report

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Action RecognitionActivity RecognitionDecoderHallucinationOptical Flow EstimationTemporal Action Localization

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