A computer implemented method, apparatus and computer program for privacy masking video surveillance data

A method of privacy masking video surveillance data, wherein the video surveillance data includes metadata associated with video data, the metadata describing objects or activity in the video data. A location of each item of metadata within its respective frame is compared with privacy mask data defining a position of a privacy mask in the frame; and based on the comparison, it is determined if the metadata is to be masked, the item of metadata being masked if so. Masking may comprise excluding metadata or flagging metadata as masked such that it is excluded by a subsequent search. A metadata item may include coordinates of a bounding box; the privacy mask may also be defined by coordinates, and coordinates of the bounding box and privacy mask may be used to determine overlaps between metadata and the privacy mask. Image data from the video data corresponding to masked search results may be retrieved.