An apparatus for identifying living skin tissue in a video sequence, the apparatus comprising: a processing unit configured to: obtain a video sequence, the video sequence comprising a plurality of image frames; divide each of the image frames into a first plurality of frame segments, wherein each frame segment is a group of neighboring pixels in the image frame; form a first plurality of video sub-sequences, each video sub-sequence comprising a frame segment from the first plurality of frame segments for two or more of the image frames; divide each of the image frames into a second plurality of frame segments, wherein each frame segment is a group of neighboring pixels in the image frame, the second plurality of frame segments comprising a greater number of frame segments than the first plurality of frame segments; form a second plurality of video sub-sequences, each video sub-sequence comprising a frame segment from the second plurality of frame segments for two or more of the image frames; analyze the video sub-sequences in the first plurality of video sub-sequences and the second plurality of video sub-sequences to determine a pulse signal for each video sub-sequence; and analyze the pulse signals for the video sub-sequences in the first plurality of video sub-sequences and the pulse signals for the video sub-sequences in the second plurality of video sub-sequences together to identify areas of living skin tissue in the video sequence. a processing unit configured to: obtain a video sequence, the video sequence comprising a plurality of image frames; divide each of the image frames into a first plurality of frame segments, wherein each frame segment is a group of neighboring pixels in the image frame; form a first plurality of video sub-sequences, each video sub-sequence comprising a frame segment from the first plurality of frame segments for two or more of the image frames; divide each of the image frames into a second plurality of frame segments, wherein each frame segment is a group of neighboring pixels in the image frame, the second plurality of frame segments comprising a greater number of frame segments than the first plurality of frame segments; form a second plurality of video sub-sequences, each video sub-sequence comprising a frame segment from the second plurality of frame segments for two or more of the image frames; analyze the video sub-sequences in the first plurality of video sub-sequences and the second plurality of video sub-sequences to determine a pulse signal for each video sub-sequence; and obtain a video sequence, the video sequence comprising a plurality of image frames; divide each of the image frames into a first plurality of frame segments, wherein each frame segment is a group of neighboring pixels in the image frame; form a first plurality of video sub-sequences, each video sub-sequence comprising a frame segment from the first plurality of frame segments for two or more of the image frames; divide each of the image frames into a second plurality of frame segments, wherein each frame segment is a group of neighboring pixels in the image frame, the second plurality of frame segments comprising a greater number of frame segments than the first plurality of frame segments; form a second plurality of video sub-sequences, each video sub-sequence comprising a frame segment from the second plurality of frame segments for two or more of the image frames; analyze the video sub-sequences in the first plurality of video sub-sequences and the second plurality of video sub-sequences to determine a pulse signal for each video sub-sequence; and analyze the pulse signals for the video sub-sequences in the first plurality of video sub-sequences and the pulse signals for the video sub-sequences in the second plurality of video sub-sequences together to identify areas of living skin tissue in the video sequence.