My iMovie video is extremely choppy, jumpy, shaky etc when I export it, how do I make it normal?

Question

Hello,
I have been using iMovie for years now, I use a HD camera, but have always imported it using large not full video. But this time I decided to go for full quality, it said playback may be bad. I assumed that when I export it all will be fine, so when ever i slow down clips in iMovie the video would be jumpy, whilst the rest of the video played very smoothly (in iMovie). But when I uploaded it to youtube it came out like this (Skip to 2 minutes in) http://www.youtube.com/watch?v=cpZnrdkpiRM
The whole video is extremly jumpy and shaky, except the slow motion parts! So I was wondering how to get the smoothness back?
Any help would be amazing, I've worked so hard and long on this and for it to be like this its very fustrating!!!
Many thanks
Josh

Answer 1

OK I was assuming that you had imported at 1920x1080, but it appears you imported at 960x540. Both would be fine as long as it is in Apple Intermediate Codec.
However, your footage is in 50P. iMovie does not normally handle 50P (although when you use it in slow motion, you are in essence using it as 25P). Set your camera to 25P and you should have no problem.
However, if you wish to try 50P in iMovie, you may be able to hack it and make it work. Also, if the current footage you are working with is irreplaceable, you can either follow the instructions below, or use an app like QuickTime Pro or MPEG Streamclip to convert it to 25P.
Here is a blog post on how someone used 50P in iMovie, although I have not tried it myself.
http://ianperegian.com/My_FZ35_38_Webpage/Edit_1080_50p_and_burn_a_disk.html