The time consumed to compute the weighting factors. The x-axis identifies Scheme  1 (the traditional matrix representation), or Scheme  2 (the proposed arraylist representation) is applied to compute the weighting factors. The y-axis is the logarithm of the time consumed by the schemes. The size of the video sequence is , and the motion vectors is obtained from T+2D MCTF. Each GOP has 32 frames. The experiment is executed on the work station with double quadcore CPUs and total 12 GB memory. The consumed time is measured by subtracting the times tamp between the beginning and the end of the process that computes the weighting factors.