Cross Correlates frames of two input clips A and B in 2D Freq domain. The orrelation is displayed in space domain as the output frame. If txt is set to 1, a valid filename with full path must be given. Limiting up to the first 1000 frames, it measures the shift between the corresponding frames of the two clips within a window of plus minus cx and cy at center of frame. Frame numbers Fn, x, y values of shifts determined within this window and fx and fy values of shift within fullframe are recorded in a text file at the end of all processing and closing of script. Normally these values should be identical but in certain repeating patterned clips clips they can be different.
This transforms data into frequency domain utilising libfftw3f-3.dll ( or, FFTW3 dll, or fftw.dll) of fftw.org being available in path.