<P>PROBLEM TO BE SOLVED: To conduct measurement of subjective quality of audio-visual stimulus. <P>SOLUTION: The subjective quality of audio-visual stimulus is measured by measuring actual synchronization errors 38s between audio and visual elements 12, 22 of the stimulus, identifying the characteristics of audio and visual cues in the stimulus 31, and generating a measure of subject quality from the errors and characteristics. The nature of the cue has an effect on the perceptual significance of a given value of synchronization error, and this can be used to relax tolerance to such errors when appropriate or to provide an accurate measure of the quality of a relevant signal as in perception by a human subject. <P>COPYRIGHT: (C)2010,JPO&INPIT 
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