1. A method of measuring the quality of audio-visual material comprising: (a) analysing the quality of an audio signal to produce an audio quality measurement; (b) analysing the quality of a video signal to produce a video quality measurement; (c) receiving a parameter indicative of the degree of motion represented by the video signal; (d) computing, from the audio quality measurement and video quality measurement, a single measurement employing one of a plurality of algorithms selected in dependence on the value of the parameter.