US 2015/0029360 A1Published application

Flicker detection method and flicker detection apparatus

AssigneeFujitsu Limited

InventorsJianrong WU, Xuan FU, Akihiro HIGASHI

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Abstract

The present invention discloses a flicker detection method and a flicker detection apparatus. The method includes: calculating the mean values of selected rows of image frames to constitute a mean value vector; calculating a differential vector between the mean value vectors of a current frame and a previous frame; calculating a DC-free difference vector; building a first square wave and a second square wave, and a third square wave and a fourth square wave; calculating a first frequency reference value; calculating a second frequency reference value; and if the difference between the first and second frequency reference values is above a threshold, then it is determined that flicker is present in the current frame; otherwise, it is determined that no flicker is present.

Claims22

Dependent claims

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.

6 more elements

A flicker detection apparatus for detecting flicker in a sequence of image frames, the apparatus comprising:

a mean value vector calculating device configured to calculate mean values of selected rows of the image frames, a calculated mean values constituting a mean value vector mean_row(k) in a order of the rows;
a differential vector calculating device configured to calculate 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;
a DC-free difference vector calculating device configured to calculate 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);
a square wave building device configured to build 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);
a first frequency reference value calculating device configured to calculate 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;
a second frequency reference value calculating device configured to calculate 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
a flicker determining device comprising a presence determination unit configured:
to determine that flicker is present in the current frame, if the difference between the first frequency reference value and the second frequency reference value is above a predetermined difference threshold;
and
to determine that no flicker is present in the current frame, if the difference between the first frequency reference value and the second frequency reference value is below or equal to the predetermined difference threshold.

8 more elements

Dependencies are inferred from the claim text.