as far as I know the FBX file format for not has the notion of quaternion.
FBX is actually a original file format, it was the internal format of an animation editing tool called Film Box how was bought by Autodesk and renamed to Motion Builder.
Their specialty is quick editing of high density motion capture key framed sequences. this is why so extensive.
anyway, I just need to figure out how to extract the information I need regardless of what options where exported.
Anyway I made more progress, I am now doing two passes, one to get the complete animation period and the on a second pass the animation is resampled as a fix rate, I am using 1/60 of a second.
then there is an optimization face that remove all of the key frame that can be interpolated from the two neighbors with is some tolerance.
The model looks much better now, but there are still other bugs I need to resolve.
if you run the demo you will see that the left leg is animated wrong, I think this is actually in my code. because before when the character was facing the camera, the same bug was of the right left, but after I applied a 180 rotation to the engine animation, now the character faces away from the camera but the the bug switched yo the left leg. somewhere there is a sign bug or maybe where the animated the model the left leg has a marrow animation, which is also a feature of animation systems when you can garb keyframes and paste of another chain of bones, but because the bones where original created by mirroring the skeleton, them the animation is play as a mirror of the flipped axis.
These are the kind of bug that you can go over the entire code and not find a single bug yet is still wrong.
anyway it is much better now but more to come.