Write an explanation about this algorithm.

Algorithm 1 Feature Extraction Input: The original RGB video frames I, pyramid level Pl, frame rate Fps, set of onecolumn intermediate images C, low-frequency cut-off Fl and high-frequency cut-off Fh of the ideal bandpass filter Output: A set of feature images S. 1: repeat 2: for each frame I do 3: Gaussian pyramid with level Pl 4: Reshape the last level to one column C0 5: end for 6: CC0 7: until size(C)=Fps 8: repeat 9: for each set C do 10: Concatenate all the columns to create a new image M 11: for each channel of M do 12: Do FFT to obtain Mf 13: Create a mask by using Fl and Fh 14: Multiply the mask by Mf to obtain N 15: Apply IFFT to N to obtain Ni 16: end for 17: merge 3 channels to obtain K 18: end for 19: SK 20: until the whole video ends 21: returnS