How to update URDF character joint state using openni_tracker

edit

I am trying to develop a simple kinect demo that consists in standing in front of a kinect and after that, start control the movents of a simple URDF character.

To do that, I planned to subscribe to the /tf topic and obtain the user's joint position and angles published by the openni_tracker node so that I could update the URDF character's joint positions according to the user's movement. Something similar to what is done in this tutorial.

How could I "convert" the quaternions published by the openni_tracker node into some understandable representation for the sensor_msgs::JointState joint_state function?

Thanks for the help!