I can't seem to figure this out, and I haven't been able to find documentation.

I'd like to be able to rotate a horizontal video into a vertical video, such that the dimensions change.

1280x720 becomes 720x1280

Any help is appreciated.

Okay, after a lot of effort and a little help, I've figured it out. Here's how to do it:

1) Find the resolution and frame rate of the video you want to rotate. In my case, it was 1280x720 and 29.9...something.

2) Open Kden live and create a new PROJECT PROFILE.
- In PROJECT SETTINGS, click the button next to the PROJECT PROFILE dropdown.
- Give it your target resolution. In my case 720x1280. I had to swap the aspect ratio too, from 16/9 to 9/16. I also had to set the frame rate.
- If you'd like, give your new project profile a name and save it. (The save button is in the top right.)

3) Import your clip and drag it to one of the video channels.

4) Add two effects to your clip: Crop-Scale-Position, and Rotate (keyframable)

5) In the Rotate effect, set "Rotate-X" to 900 (or 2700).

6) In Crop, Scale, Position, play with Scale X and Scale Y so that your clip fills the frame. For some reason, 90, 90 was enough. I didn't need 100, 100. Not sure why.

7) Also in Crop, Scale, Position, play with "Tilt X" and "Tilt Y". This positions your clip. I have no idea why these fields aren't called "Pos X" and "Pos Y", but they aren't. Also, I can't figure out what the number means. For me X 212, and Y 380 put the upper left corner of the clip in the upper left corner of the frame. Make small changes to these number to figure out which directions the clip will move.

You sort of have to do 6) and 7) simultaneously to expand your clip to the correct size and position it so that it fills the frame. I suppose you could also figure out what the numbers mean and work everything out with some arithmetic. If you do know what the numbers mean, please post a comment here.

Good luck!

Addendum: Unfortunately, even when I follow this process, the resulting videos are full of hieroglyphs.

My conclusion is that I this is too hard with KdenLive. But the good news is that it seems to work pretty easily with VLC. My workflow will now be rotating clips with VLC, and then using VLC to patch them together and manage sounds and transitions.