MediaEval is a benchmarking initiative dedicated to evaluating new algorithms for multimedia access and retrieval. It emphasises the 'multi' in multimedia and focuses on human and social aspects of multimedia tasks. 
VideoSense organized the Visual Privacy Task within the MediaEval Grand Challenge 2013 which took place in Barcelona, Spain, on 18-19 October 2013.

This task aims to find ways to protect the privacy of people in video surveillance data. Participants were invited to propose methods to obscure elements in the image which carry information about the identity of subjects. Some examples include faces, ethnicity, gender, and accessories.

MediaEval2013

The evaluation was carried out by considering three complementary axis, namely the level of privacy protection guaranteed by the filter, the intelligibility (amount of retained information left after applying the filter in order to keep the video understandable) and whether the result was visually acceptable.

Each participant was given pre-annotated sequences from the PEViD dataset, provided by EPFL and annotated by all VideoSense partners.

The proceedings of the workshop are available online: http://ceur-ws.org/Vol-1043/

Here there are some examples of the proposed approaches.

              MediEvalProposedApproach1 MediEvalProposedApproach2 

              MediEvalProposedApproach3 

               MediEvalProposedApproach4