I can create reponsive video by using width="100%" and height="100%" in older JW player plugin. Now it didn't work in new plugin. I can not even save the width setting to 100% in player management. See what happened in my page http://thaikm4u.com/rajamobile/?p=352 .The first video frame uses JW player. When you resize browser to smaller size the frame in <div>..</div> do the responsive work well but not the video. Please compare with the second video frame using MediaElement.js it works well responsively.
I can create responsive video with old JW Player plugin with the help from this site http://www.lahive.co.uk/responsive-wordpress-jw-player/