Patent ID: 8358375

Claim:
A method for measuring a time difference between digital signals and digital audio signals comprises the steps of: reading a video frame; extracting an image of the designated part in said video frame; acquiring an interpolated frame for each time corresponding to a time resolution needed for the measurement by inter-frame interpolation; wherein, frames configuring said digital video signals being subjected to a process including the steps of: acquiring amplitude domain difference for each frame configuring the basic video signals; acquiring a space frequency spectrum by two-dimensional Fourier transform of each differential frame; taking out a low-pass component of said space frequency spectrum, thereby considering said low-pass component to be a time series frequency of said basic video signals; wherein, said digital audio signals accompanied with said digital video signals being subjected to a process including the steps of: removing a high frequency component by passing through a low-pass filter; acquiring a frequency spectrum by short-time window one-dimensional Fourier transform so as to provide samples at every time corresponding to a time resolution needed for the measurement; taking out a low-pass frequency spectrum from said frequency spectrum, thereby considering said low-pass component to be a time series frequency of said basic audio signals; calculating a cross-correlation coefficient for said time series frequency of said basic video signals and said time series frequency of said basic audio signals to provide the maximum value of said cross-correlation coefficient for a time series data of the frequency domain of said basic video signals and a time series data of the frequency domain of said basic audio signals; statistically identifying the time difference between said digital video signals and said digital audio signals from the number of time series samples providing said maximum value.