If you're not required to use JMF, it is probably worthwhile to consider other options at this point. Unfortunately, Xuggle/Xuggler is apparently on hiatus - but if the state of its last release will work for you, they have a Frame Capture Demo that should be a good starting point.
If you are sticking with JMF, perhaps Accessing Individual Decoded Video Frames will point you in the right direction with its info on using a pass-through codec. Note that you'll need to search for a copy of FrameAccess.java if you want the demo code for this option (the link seems to be broken on that page).