Why subtract 'new_length' to calculate 'average_duration' ?

Hi. Why do you subtract 'new_length' from 'num_frames' and then divide by 'num_segments' to calculate 'average_duration' ? Can we not directly divide 'num_frames' by 'num_segments' to get the 'average_duration' ? Thanks!

tsn-pytorch/dataset.py

Line 66 in 2f0468e

    
           average_duration = (record.num_frames - self.new_length + 1) // self.num_segments