1. A method for assessing the presence of a watermark in a video, wherein said video comprises at least a sequence of frames, the method comprises for at least one frame among one of the sequences of frames: computing a set of axial cross-correlation values, each axial cross-correlation value corresponding to a correlation between said frame and a reference watermark shifted along a spatial horizontal axis; obtaining a detection score by computing a weighted sum of values output by a function applied to said axial cross-correlation values; and assessing the presence of a watermark according to the detection score.