Foreground motion detection in compressed video data

Technologies are generally described to identify foreground motion detection in compressed video data. In some examples, a foreground motion detection module may determine transform-coefficient-magnitude sums and motion-vector-magnitude sums associated with block coding units (BCUs) in compressed video data without decompressing the video data. The foreground motion detection module may also determine a background mean and a background co-variance associated with the compressed video data. To determine whether the BCU(s) contain foreground motion, the foreground motion detection module may determine a statistic based on the transform-coefficient-magnitude sums, the motion-vector magnitude sums, the background mean, and the background co-variance and compare the statistic to a threshold.