pme
Rotating videos from portrait to landscape & vice versa:
For several years I've been using a freeware video manipulator called MPEG Streamclip. TIL you can use it to rotate videos through stages of 90 degrees, both clockwise & counter-clockwise.
I captured a number of short 1080p videos on my DLSR last week, some of those had been done in portrait orientation and were displayed in landscape in the Photos app.
So I exported them to the desktop & opened each one in succession with MPEG Streamclip. Under Edit on the menubar I chose to rotate them CCW through 90 degrees. Then I used "Save As…" to save the edited versions.
When re-imported into Photos app, they were displayed in their correct portrait orientation.
They were historical working steam engines, which tend to be taller rather than long, so the portrait orientation was a more natural choice.