A method of extracting a key frame from a sequence of frames constituting a shot, each frame being constituted by a matrix of pixels, comprises: for each frame of the sequence of frames: computing (3) the optical flow of the frame compared to the following frame as a matrix of displacement of each pixel from the frame to the following frame; computing (5) a motion entropy measure based on the optical flow of the frame; selecting (7) as key frame the frame of the sequence of frames having the maximum motion entropy measure.