Questions about charades_video_tsn.py

Thank you for sharing the code. It help a lot.
But there is some confusion about the data loading procedure in **charades_video_tsn.py**.
Here is the codes：
``

n = self.data['datas'][index]['n']
if shift is None:
shift = np.random.randint(n-self.train_gap-2)
else:
shift = int(shift * (n-self.train_gap-2))
ss = [shift] + [np.random.randint(n-self.train_gap-2)
for _ in range(self.segments-1)]

``
In this way, ss would be a list including indexes of images to be loaded. But I find the values in ss not regular, which seems not consistent with TSN.
Did I miss something? By the way, what's the difference among **charades_tsn.py**, **charades_video.py** and **charades_video_xx.py**?
Looking forward to your reply.