CrossNet: Cross-Scene Background Subtraction Network via 3D Optical Flow

This paper investigates an intriguing yet unsolved problem of cross-scene background subtraction for training only one deep model to process large-scale video streaming. We propose an end-to-end cross-scene background subtraction network via 3D optical flow, dubbed CrossNet. First, we design a new motion descriptor, hierarchical 3D optical flows (3D-HOP), to observe fine-grained motion. Then, we build a cross-modal dynamic feature filter (CmDFF) to enable the motion and appearance feature interaction. CrossNet exhibits better generalization since the proposed modules are encouraged to learn more discriminative semantic information between the foreground and the background. Furthermore, we design a loss function to balance the size diversity of foreground instances since small objects are usually missed due to training bias. Our whole background subtraction model is called Hierarchical Optical Flow Attention Model (HOFAM). Unlike most of the existing stochastic-process-based and CNN-based background subtraction models, HOFAM will avoid inaccurate online model updating, not heavily rely on scene-specific information, and well represent ambient motion in the open world. Experimental results on several well-known benchmarks demonstrate that it outperforms state-of-the-art by a large margin. The proposed framework can be flexibly integrated into arbitrary streaming media systems in a plug-and-play form.