Abstract:

We present a psychophysical and analytical framework formotion activity descriptors computed from compressed domain block motion vectors. In the first analysis, we quantize the descriptors and show that they perform well against the ground truth. The MPEG-7 motion activity descriptor is also among the best performers. In the second analysis, we examine the specific cases where each descriptor fails, using a novel pair-wise comparison method. The analytical measures verestimate or underestimate the intensity of motion activity under strong camera motion or extreme camera angles. We finally discuss the experimental methodology and analysis methods we used, and possible alternatives. We review the applications of motion activity and how our results relate to them.