Inexpensive high dynamic range video for large scale security and surveillance

Abstract-We describe a new method for High Dynamic Range (HDR) Video using alternating exposures that adds no additional cost or bandwidth requirements to individual IP cameras, making it suitable for large scale security and surveillance systems. Sufficient dynamic range is crucial to the efficacy of a surveillance system, as saturated pixels mean a camera can no longer "see" its surrounding environment. High costs associated with hardware for improved dynamic range make them unsuitable for very large networks with hundreds or even thousands of cameras. We outline a scalable software method that uses post-processing to combine the information in adjacent frames of a video sequence captured with alternating short and long exposures. In particular, we introduce a novel bi-directional motion estimation module that utilizes block-based motion vectors to register frames with large differences in global brightness and fast local motion within saturated regions. An HDR post-processing solution can be deployed at a central location to process individual camera streams on an "as needed" basis, removing additional costs at the device-end. Furthermore, cameras continue to transmit low dynamic range frames, so there is no additional bandwidth requirement. Results show significant gains in video quality for inexpensive cameras when exposed to brightness variations common in security and surveillance