ow to estimate velocity from robot_pose_ekf

I have a differential drive mobile robot. and I am using robot_pose_ekf to estimate the state of the robot [x,y,θ]

How to estimate [v,ω ] the translational and rotational velocities. from robot_pose_ekf output or adding [v,ω ] as an output from robot_pose_ekf [x,y,θ,v,ω]  .
