Method of reducing digital video flicker
Methods of reducing digital video flicker, and related systems, devices and computer program products are provided. A method of reducing human-perceivable flicker in a digital video is provided, in which video frames are recorded unevenly with respect to time and in synchronization with a lighting flicker frequency. A system including a camera and a computer is provided, the system configured to reduce human-perceivable flicker in a digital video, in which video frames are recorded unevenly with respect to time and in synchronization with a lighting flicker frequency, so as to reduce human-perceivable flicker in a video assembled using the computer from the video frames.
1. A method for reducing human-perceivable flicker during playback of a digital video, recorded at an illumination intensity, the illumination intensity varying at a lighting flicker frequency and having a constant time-averaged illumination intensity, the method comprising, during a plurality of cycles of video recording within which video frames are recorded unevenly with respect to time, and all video frames during the plurality of cycles are captured either in synchronism with a phase of the lighting flicker frequency or 90 degrees out of phase with the lighting flicker frequency:
capturing, during the plurality of cycles, a plurality of first frames in synchronism with the phase of the lighting flicker frequency and such that there is a first time interval between a first pair of successive first frames of the plurality of first frames and a second time interval, different from the first time interval, between a second pair of successive first frames of the plurality of first frames;
capturing, during the plurality of cycles, at least one second frame 90 degrees out of phase with respect to the phase of the lighting flicker frequency; and
applying image processing, the image processing comprising applying a compensation gain to the at least one second frame to compensate for a difference in brightness between the plurality of first frames and the at one second frame.
2. The method of claim 1 , comprising:
determining an interval between capturing a first frame of the plurality of first frames and capturing a second frame of the at least one second frame, the second frame subsequent to the first frame; and
implementing the interval by setting a corresponding V blanking value.
3. The method of claim 1 , comprising assembling the digital video for playback with the plurality of first frames and the at least one second frame being equally spaced in time.
4. The method of claim 1 , comprising:
determining a geographic position using a position determining system; and
determining the lighting flicker frequency based on the geographic position.
5. The method of claim 1 , wherein
the lighting flicker frequency is double a local mains frequency, the local mains frequency being a user settable parameter for use in video recording.
6. The method of claim 1 , wherein the lighting flicker frequency is 120 Hz.
7. The method of claim 1 , wherein the lighting flicker frequency is 100 Hz.
8. A system for reducing human-perceivable flicker during playback of a digital video recorded at an illumination intensity, the illumination intensity varying at a lighting flicker frequency and having a constant time-averaged illumination intensity, the system comprising a computer configured to control a video camera to, during a plurality of cycles of video recording within which video frames are recorded unevenly with respect to time, and all video frames of the plurality of cycles are recorded either in synchronism with a phase of the lighting flicker frequency or 90 degrees out of phase with the lighting flicker frequency:
capture, during the plurality of cycles, a plurality of first frames in synchronism with the phase of the lighting flicker frequency and such that there is a first time interval between a first pair of successive first frames of the plurality of first frames and a second time interval, different from the first time interval, between a second pair of successive first of the plurality of first frames;
capture, during the plurality of cycles, at least one second frame 90 degrees out of phase with respect to the phase of the lighting flicker frequency; and
apply image processing, the image processing comprising applying a compensation gain to the at least one second frame, to compensate for a difference in brightness between the plurality of first frames and the at least one second frame.
9. The system of claim 8 , wherein the computer is further configured to control the video camera to:
determine an interval between capturing a first frame of the plurality of first frames and capturing a second frame of the at least one second frame, the second frame subsequent to the first frame; and
implement the interval by setting a corresponding V blanking value.
10. The system of claim 8 , wherein the computer is further configured to control the video camera to assemble the digital video for playback with the plurality of first frames and the at least one second frame being equally spaced in time.
11. The system of claim 8 , wherein the computer is further configured to control the video camera to:
determine a geographic position using a position determining system; and
determine the lighting flicker frequency based on the geographic position.
12. The system of claim 8 , wherein
the lighting flicker frequency is double the local mains frequency, the local mains frequency being a user settable parameter for use in video recording.
13. The system of claim 8 , wherein the lighting flicker frequency is 120 Hz.
14. The system of claim 8 , wherein the lighting flicker frequency is 100 Hz.