Hi,
Some codecs don't like being played backwards, or any other way than realtime forwards really. A Quicktime encoded with Photo JPEG or PNG might be worth a shot.
I had great success with HAP encoded files and https://github.com/bangnoise/ofxHapPlayer
What I needed to do was to set the frame of the movie to anywhere I wanted, it was a movie of a guy on a turntable and I needed to be able to rotate it with the mouse. Not quite the same as what you need, but if that works I can't see it being too hard to do what you need, if it doesn't support it already.
