We have executed the example 14-5 of the Manual Image Processing (vol.2) to test OpticalFlowPyrLK with the Yosemite (images of 252x316 pixels). We have used the following values for the input parameters: (1) A Gaussian kernel of length 5: 151, 21186, 5319, 2186, 151 (2) Levels from 1 to 3 (numLevel) (3) rate =2 (4) winSize of 3, 5 and 7 (5) numIter of 1,2 and 3 (6) Theshold=0 (7) prevPt is initialized by using: for (i=0;i prevPt.x=i%roiSize.width; prevPt.y= i/roiSize.width; } Then, the flow is obtained for all the pixels. (8) nextPt is equal than prevPt. We obtain 2879.2 cycles per pixel (in the input image) with a Gaussian filter of length 5, numLevel=1, numIter=1, winSize=3 (cycles of the processor clock obtained with instruction rdtsc). This is a high value. With other combination the number of cycles is yet higher. Nevertheless, with the IPPtest programps_ippcvem64t.exe we obtain 10 , 6, or 2 clocks per element (depends on the input parameters) for images of 256x256 pixels. What are we doing wrong? Is the source code for ps_ippcvem64t.exe available? We cannot reproduce the clocks per element of this test (we suppose clocks per element are cycles per pixel in this context).