
{"publication_number": "US-6600784-B1", "abstract": "a method describes motion activity in a video sequence . a motion activity matrix is determined for the video sequence . a threshold for the motion activity matrix is determined . connected regions of motion vectors at least equal to the threshold are identified and measured for size . a histogram of the distribution of the sizes of the connected areas is constructed for the entire video sequence . the histogram is normalized to characterize the spatial distribution of the video sequence in a motion activity descriptor .", "application_number": "US-49670700-A", "description": "fig1 shows a method 100 for describing the spatial distribution of motion activity according to our invention . we determine the average motion vector magnitude per macro - block ( c mv avg ) of a video frame or video object by taking the average of the magnitudes of block motion vectors in p frames of a compressed video sequence . this process is described in u . s . patent application ser . no . 09 / 236 , 838 \u201c method of feature extraction of video sequences \u201d filed by divakaran et al . on jan . 25 , 1999 incorporated herein by reference . in short , for each video frame or object of a video sequence 101 , step 110 determines a motion activity matrix c mv 102 : c mv ={ r ( i , j )