I've just worked out how to do this, makes upgrading to Quicktime Pro worthwhile.
- Take your Quicktime Jump back movie and open in Quicktime Pro (£20 upgrade from regular Quicktime). We'll call the screen that opens Screen X
- Click window then Show movie properties from the drop down menu
- Click soundtrack and then click delete
- Click the Video track and click extract (this will open the video again in a new screen which we will call screen Y)
- Click edit, select all, copy. then click on the movie screen and click paste.
- Drag the right half triangle on the time bar at the bottom to the end so that the whole time bar is highlighted.
- Go to the original movie screen X and click edit, select all, copy and then you can close this screen X as you wont need it anymore, no need to save changes.
- Go to back to the other screen Y, click edit then click Add to selection and scale.
- This Screen (Y) should now play a slow mo version of your original jump back movie.
- Save as Jump back Slow mo
Love this, just done a slow-mo version of my rolling GARBHA PINDASANA, funny.
PS. Anyone recommend anywhere to practice in Manchester UK?