results of the average of black window
| BLC_R3_MEAN | this field represents the average black value of bottom right channel |
| BLC_R2_MEAN | this field represents the average black value of bottom left channel |
| BLC_R1_MEAN | this field represents the average black value of top right channel |
| BLC_R0_MEAN | this field represents the average black value of top left channel |