960 fps is only a software process. Therefore, it is done only with stock application. However, Filmic Pro application can shoot longer with 120 or 240 fps. However, auto focus does not work.
Official Miui v18.104.22.168 EEA
At least 2 hours Instagram (1.53GB data)
Screen off 1:30 hours of music (Local)
About 3 hours Chrome (150MB data)
I did not pay much attention to the duration of others, but an ordinary use.
The problem was with the latest DM Verity encryption that came to my mind. As a result of long efforts, I turned off DV-Verity and device encryption and the problem disappeared.
This problem (Pro mode) is only experienced in the European version of the E E A Miui 22.214.171.124 QFAEUXM