Patent ID: 9167175
Filing Date: 2015-10-20
Classification: H04N

Abstract:
1. A flicker detection method of detecting flicker in a sequence of image frames, the method comprising: calculating mean values of selected rows of the image frames, the calculated mean values constituting a mean value vector mean_row(k) in an order of the rows; calculating a differential vector diff_frame(k) between the mean value vector mean_row(k) of a current frame and the mean value vector mean_row(k−1) of a previous frame; calculating a DC-free difference vector diff_mean_row(k) by subtracting a direct current component of the differential vector diff_frame(k) from respective elements of the differential vector diff_frame(k); building a first square wave and a second square wave with a first frequency and phases differing by 90 degrees, and a third square wave and a fourth square wave with a second frequency different from the first frequency and phases differing by 90 degrees, each of the first to the fourth square waves having a specific number of elements per cycle and a same length as the DC-free difference vector diff_mean_row(k); calculating a sum of an absolute value of a dot product of the DC-free difference vector diff_mean_row(k) and the first square wave and the absolute value of the dot product of the DC-free difference vector diff_mean_row(k) and the second square wave as a first frequency reference value; calculating the sum of the absolute value of the dot product of the DC-free difference vector diff_mean_row(k) and the third square wave and the absolute value of the dot product of the DC-free difference vector diff_mean_row(k) and the fourth square wave as a second frequency reference value; and if a difference between the first frequency reference value and the second frequency reference value is above a predetermined difference threshold, it is determined that flicker is present in the current frame; otherwise, it is determined that no flicker is present in the current frame.