how can I rotatre a video 90 degrees

http://www.thelinuxblog.com/rotating-videos-in-linux/

   David
   in TN

I believe the instructions on the aforementioned webpage describe how to permantly rotate the video or create a copy of the video which is rotated.

If you want the video player, itself, to rotate the video, then I imagine the method varies depending on which video player you are using. I do not see any available options in Totem that allow rotating video. But with VLC you can rotate video, with VLC open, press Crtl + e, or click on Tools > Effects and Filters, click on the box next to Rotate which enables the rotating pointer. You can then rotate the pointer and thus the video to the desired orientation.