Scrambling for Privacy Protection in Video Surveillance Systems

In this paper, we address the problem of privacy protection in video surveillance. We introduce two efficient approaches to conceal regions of interest (ROIs) based on transform-domain or codestream-domain scrambling. In the first technique, the sign of selected transform coefficients is pseudorandomly flipped during encoding. In the second method, some bits of the codestream are pseudorandomly inverted. We address more specifically the cases of MPEG-4 as it is today the prevailing standard in video surveillance equipment. Simulations show that both techniques successfully hide private data in ROIs while the scene remains comprehensible. Additionally, the amount of noise introduced by the scrambling process can be adjusted. Finally, the impact on coding efficiency performance is small, and the required computational complexity is negligible.

I. Introduction

Video surveillance systems are omnipresent nowadays, with large systems in use in strategic places such as public transportation, airports, city centers, or residential areas. The prevailing sense of insecurity at the beginning of this century, with terrorist threats and high criminality, renders the intensive use of video surveillance tolerable despite its Orwellian big brother nature. However, people have a legitimate fear of this invasion of their personal privacy, with this objection slowing down a wider acceptance of video surveillance systems.