I was recently doing some video editing work where the workflow was something like this: film in portrait, transfer to computer, rotate videos by 90 degrees, sequence together several videos, strip out background noise from entire video. Filming was done with a camera, sequencing was done by Kdenlive (I've previously only had experience with Blender's VSE and I must say I was very happy with this new application), and the noise-stripping was done with Audacity. I must say I'm surprised at how fast this was all accomplished and kudos to all those developers who created these apps.
However one thing I didn't know how to do was how to rotate the video by
90 degrees. Kdenlive can do it but it ends up being awkwardly stretched
and I couldn't figure out how to unstretch it. Luckily mencoder, which
comes with the mplayer package, has got a few tricks up its sleeve.
More for my own records than for anybody else, here's the command I used:
$ mencoder -vf rotate=2 -o output.avi -oac pcm -ovc lavc input.mov
As my input file was a .mov some of the sound wasn't synchronised well
after rotating, which was easily fixed by this option -demuxer mov. If
you want to rotate clockwise instead of anticlockwise change rotate=2
to rotate=1.