Improved blotch detection by postprocessing

Blotches are common artifacts in old film sequences that manifest themselves as disturbing bright or dark spots. Existing methods for detecting blotches can achieve high detection rates. High detection rates are only useful if the corresponding number of false alarms is not too high, visible artifacts in the corrected sequence result otherwise. We show that the performance of blotch detectors can be improved significantly by taking statistical influence of noise on the detection mechanism into account. Further improvements are achieved first by using a double-stage detection strategy and second by a constrained dilation technique