Privacy-Enabled Object Tracking in Video Sequences Using Compressive Sensing
In a typical video analysis framework, video sequences are decoded and reconstructed in the pixel domain before being processed for high level tasks such as classification or detection.Nevertheless, in some application scenarios, it might be of interest to complete these analysis tasks without disclosing sensitive data, e.g. the identity of people captured by surveillance cameras. In this paper we propose a new coding scheme suitable for video surveillance applications that allows tracking of video objects without the need to reconstruct the sequence,thus enabling privacy protection. By taking advantage of recent findings in the compressive sensing literature, we encode a video sequence with a limited number of pseudo-random projections of each frame. At the decoder, we exploit the sparsity that characterizes background subtracted images in order to recover the location of the foreground object. We also leverage the prior knowledge about the estimated location of the object, which is predicted by means of a particle filter, to improve the recovery of the foreground object location. The proposed framework enables privacy, in the sense it is impossible to reconstruct the original video content from the encoded random projections alone, as well as secrecy, since decoding is prevented if the seed used to generate the random projections is not available.