4. The method defined in claim 3 , wherein each of the query data elements is associated with a respective one of the video frames in the query video stream, and wherein said deriving the set of query data elements comprises, for each particular video frame in the query video stream: extracting at least one feature for each of a plurality of regions of the particular video frame in the query video stream, wherein the query data element associated with the particular video frame in the query video stream comprises the at least one extracted feature.
4. The method defined in claim 3 , wherein each of the query data elements is associated with a respective one of the video frames in the query video stream, and wherein said deriving the set of query data elements comprises, for each particular video frame in the query video stream: extracting at least one feature for each of a plurality of regions of the particular video frame in the query video stream, wherein the query data element associated with the particular video frame in the query video stream comprises the at least one extracted feature. 12. The method defined in claim 4 , wherein at least one feature for at least one region of the video frame in the reference video stream is temporally normalized and wherein at least one feature for at least one region of the video frame in the query video stream is temporally normalized.