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Transform domain based image / video privacy protection

This paper presents a novel method for protecting privacy sensitive regions inside a digital frame. The purpose is achieved by deteriorating the visual quality of privacy sensitive region by adding probability model based random noise to nonzero quantized transform coefficients of the region. The probabilistic model based noise is generated based on the information from neighboring macroblocks and added only to selective non zero AC transform coefficients to have minimal impact on bit rate. Moreover, the parameters of the probability model are derived from the neighboring blocks inside the frame such that the noise follows characteristics of the frame content. For the purpose of implementation, we used H.264/AVC video coding standard for videos and JPEG image compression standard for images. The probabilistic model based noise is generated using a secret key, which can be shared with the authorized decoder such that the obfuscated region can be completely recovered. In order to limit drifting of obfuscation effect outside the targeted regions, Inter and Intra prediction blocks inside H.264/AVC encoder were modified. Overall, we achieve good obfuscation of selected regions with minimal impact on coding efficiency with the capability to achieve complete reconstruction at the authorized decoder.