The 64 x 128 pixel detection window will be divided into 7 blocks across and 15 blocks vertically, for a total of 105 blocks. Each block contains 4 cells with a 9-bin histogram for each cell, for a total of 36 values per block. This brings the final vector size to 7 blocks across x 15 blocks vertically x 4 cells per block x 9-bins per histogram = 3,780 values.