Patent ID: 7555046

Claim:
A method for detecting events in a video sequence, said method comprising the steps of: providing a video sequence; sampling the video sequence at regular intervals to form a series of snapshots of the sequence; measuring a similarity of each snapshot; measuring a similarity change between successive pairs of snapshots, wherein if a similarity change magnitude is greater than a predetermined threshold, a change event has been detected; verifying the change event to exclude a false positive, wherein a false positive includes an occlusion; eliminating an occlusion by weighting a time derivative of the similarity measure according to the definition f w ⁡ ( t ) = g ⁡ ( t ) * S . w ⁡ ( t ) ⁢ ⁢ wherein g ⁡ ( t ) = h ⁡ ( min i ∈ [ n 1 , n 2 ] , j ∈ [ n 1 , n 2 ] ⁢ similarity ⁡ ( w t - i , w t + j ) ) , wherein similarity ⁡ ( w i , w j ) = 1 n ⁢ ∑ k = 1 n ⁢  hist i ⁡ [ k ] - hist j ⁡ [ k ]  , and wherein {dot over (S)} w (t) is the similarity measure time derivative, w i , w j are corresponding windows-of-interest in a pair of successive snapshots, [n 1 ,n 2 ] is the duration neighborhood about the snapshot incorporating the occlusion over which similarity is being sought, h is a positive increasing function with h(1)=1, and hist is a histogram of spatial intensity values in the window-of-interest; and completing the processing of the snapshot incorporating the verified change event.