Capturing video with a 7D II vs 70 D

[shutterdown]

I was taking video of a family event and used both these cameras at the same time, from different angles.

The 7D II produced two files. They both added up to about 30 minutes. One of the files was about 18 minutes. The settings were FHD 29.97P IPB.

The 70D produced 5 files. As before, they added up to about 30 minutes. The settings were 1920 30 ALL-I.

Both cameras in P, on the mode dial. Both taking MOV.

At first, I thought that the 7D had shut down prematurely, due to, perhaps, heating up or low battery. However, the battery was still good and the camera was not confined.

Why is the file size smaller on the 7D? Compression of the video?

[Busted Knuckles]

All-I does not borrow any pixels from the prior frame. IPB uses unchanged pixels from prior frame(s).