How to add speed controls to Jwplayer

Question

I want to add speed controls like 1x, 2x etc. to my jwplayer. I am using jwplayer 7

Plz suggest how to do it.

here is Code:

<div id="videoelement"></div>
jwplayer("").setup({
            'id': 'playerID',
            'file': "some.mp4",
            'flashplayer': '/Scripts/JWPlayer/jwplayer.flash.swf',
            'html5player': '/Scripts/JWPlayer/jwplayer.html5.js',
            'primary': 'flash',
            'autoBuffering': 'true',})