According to an aspect, there is provided an apparatus for identifying living skin tissue in a video sequence, the apparatus comprising a processing unit configured to receive a video sequence, the video sequence comprising a plurality of image frames； divide each of the image frames into a plurality of frame segments, wherein each frame segment is a group of neighboring pixels in the image frame； form a plurality of video sub-sequences, each video sub-sequence comprising a frame segment from two or more of the plurality of image frames； analyze the plurality of video sub-sequences to determine a pulse signal for each video sub-sequence； determine a similarity matrix based on pairwise similarities for each determined pulse signal with each of the other determined pulse signals； and identify areas of living skin tissue in the video sequence from the similarity matrix.
