Canon EOS R6 Mark II Mirrorless Camera with 24-105mm f/4-7.1 Lens - Manual (Page 609)

Changing Movie Orientation Information
You can manually edit movie playback orientation information (which determines which side
is up).
1.
Select [ : Change mov rotate info].
2.
Select a movie.
Turn the < > dial to select a movie with orientation information to
change.
609