1. A picture quality diagnostic apparatus comprising: means for generating a human vision model response for a test input video signal based on a human vision model; means for applying to the human vision model response an objective measures map based on the test input video signal for different impairment types as a mask to produce an objectively filtered subjective map; and means for determining from the objectively filtered subjective mask an impairment analysis to give respective proportions of the different impairment types.