You have 3 options if your video uses MotionJPEG compression and you are having problem using that footage in Premiere Elements 12.
This is a frequent problem for Premiere Elements (any version). It is a toss up whether the codec is really missing or whether or not it is
just not recognized by Premiere Elements (any version).
Remedies in my order of my preference
1. If you have a utility software that came with the camera, install it in the hope that it will install the necessary and recognizable MotionJPEG codec.
2. Download tryout (purchase if it solves the problem) the Morgan MotionJPEG codec
3. Conversion to another format..since your frame size is 448 x 336 4:3, we need to talk about the destination for the export.